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Re: New Vintage Computer Forum and a question

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  • alltare
    Erik, These questions/comments come to mind: How are you booting the 8800? Are you directly addressing and executing the boot PROM, using a turnkey board with
    Message 1 of 11 , May 6, 2003
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      Erik,

      These questions/comments come to mind:

      How are you booting the 8800? Are you directly addressing and
      executing the boot PROM, using a turnkey board with Turmon PROM, or
      what?

      What boot PROM are you using (DBL, MDBL, ...)?

      MITS had two 8" disk "formats"- the original and the later "NWD" (New
      Write Delay) format. There were several timing changes to the
      controller boards and therefore to the recorded data. I think you
      have a paper giving the various timing differences. You may be using
      relatively incompatible controller/diskette combinations that totally
      fail to work right in the 8800. I think all model B's were supplied
      with NWD controllers, and almost all 8800s had controllers with the
      original pre-NWD timing.

      How much RAM is in the 8800? Are you sure all RAM is good? You
      should probably have at least 32K of good memory (beginning at
      address 0) to load later versions of BASIC. Try readdressing your
      RAM boards or swapping with those known good ones from the 8800BT.
      On MITS' 16K boards, they had real problems with the 4-position DIP
      switches used for addressing (dirty contacts with resistance of a few
      ohms)- often the switches would be replaced with soldered jumpers as
      a cure. Try restricting max RAM to no more than 48K.

      Because of the noisy buss, put all RAM as physically close as
      possible to the CPU board.

      The code in those old 1702 EPROMs can become corrupted after almost
      30 years. Try using the apparently good boot PROM from the BT in the
      8800. If you're using chips that you bought from altairmanuals.com,
      they should still be good for a long time to come unless you remove
      the sticker from the erasure window.

      Even if you do have a bad serial I/O board for your terminal, you
      should still see the disk's head stepping from track to track as it
      boots. The boot ROM doesn't check for the presence of a terminal or
      even an I/O board like modern PCs do. Since the head doesn't move
      after loading, I think the problem is not the serial board.

      Steve
      =========================

      --- In altaircomputerclub@yahoogroups.com, ErikSKlein <no_reply@y...>
      wrote:
      > Hello all,
      >
      > I just found this group while poking away at the net. I'm glad
      > there's a community of Altair users/collectors. . .
      >
      > First off, I have a Vintage Computer Collecting forum that I
      started
      > as an extension of my website at www.vintage-computer.com/vcforum.
      > It has been accessible for about a week now and we've already got
      > over 120 posts. I'm hoping that by getting the word out we can
      > create a dynamic community.
      >
      > I encourage you to head over and take a look.
      >
      > Now, my question:
      >
      > As part of my collection I have an Altair 8800 (actually 2, but one
      > is being rebuilt) and an Altair 8800BT.
      >
      > The 8800BT came with a pair of MITS 8" drives (Pertec drive, MITS
      > controller in the drives and machine) and it works perfectly. Turn
      > the key and the machine boots to a prompt.
      >
      > The 8800 came with the same setup but never booted. I recently
      tried
      > a few things to figure out where the problem was.
      >
      > First of all, I tested the 8800 set of disk controller boards in
      the
      > working 8800bt system and I have and determined that the cards are
      > not the problem. (The drives that came with the 8800 aren't quite
      > functional, but they are close)
      >
      > I then returned my attention to the original 8800 with its
      > controller cards hooked up to the pair of known-good drives. For
      the
      > life of me I can't get this machine to function properly. I have no
      > idea why it won't boot, but it won't. It goes through the motions;
      > it enables the boot drive and loads the heads but it won't output
      > anything to the terminal.
      >
      > I suspected the serial card until I ran a test on that and was able
      > to get it to spit data out from the proper output port. I've tested
      > every other aspect of the system, within reason, and the machine
      > appears to be fine. It just won't cooperate with me about booting.
      > I'm at my wits end trying to boot this machine.
      >
      > Does anyone have any suggestions about what I can try next? I'd
      > really like to have the 8800 boot from the drives someday. . .
      >
      > Erik
    • Erik Klein
      I ve inserted my responses below. Hopefully the formatting isn t too screwy. alltare wrote: Erik, These questions/comments come to
      Message 2 of 11 , May 6, 2003
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        I've inserted my responses below. Hopefully the formatting isn't too screwy.

        alltare <no_reply@yahoogroups.com> wrote:
        Erik,

        These questions/comments come to mind:

        How are you booting the 8800? Are you directly addressing and
        executing the boot PROM, using a turnkey board with Turmon PROM, or
        what?

        [ESK] I am directly addressing the boot prom. I'm pretty sure it's at 177000 so I turn the machine on, raise stop and reset simultaneously, raise the first 8 switches (A15-A8) and raise Examine. I then "run."

        [ESK] I've tried several variations of sense switch settings with the above (set after examine, before I run)

        What boot PROM are you using (DBL, MDBL, ...)?

        [ESK] I am using a DBL PROM. I have at least two versions of this, one of which seems to match up to the 4.1 version in the 8800BT I have.

        MITS had two 8" disk "formats"- the original and the later "NWD" (New
        Write Delay) format. There were several timing changes to the
        controller boards and therefore to the recorded data. I think you
        have a paper giving the various timing differences. You may be using
        relatively incompatible controller/diskette combinations that totally
        fail to work right in the 8800. I think all model B's were supplied
        with NWD controllers, and almost all 8800s had controllers with the
        original pre-NWD timing.

        [ESK] I have two sets of functional controllers between the 8800 and the 8800BT. Both work on the drives and disk as attached to the 8800BT, neither works on the 8800.

        How much RAM is in the 8800? Are you sure all RAM is good? You
        should probably have at least 32K of good memory (beginning at
        address 0) to load later versions of BASIC. Try readdressing your
        RAM boards or swapping with those known good ones from the 8800BT.
        On MITS' 16K boards, they had real problems with the 4-position DIP
        switches used for addressing (dirty contacts with resistance of a few
        ohms)- often the switches would be replaced with soldered jumpers as
        a cure. Try restricting max RAM to no more than 48K.

        [ESK] I've got anywhere between 32 and 56K in the machine at any time when I've been doing testing. I'm pretty sure that all of the RAM is good although I haven't tested every bit. I may swap over the 3 16MCDs from the BT to the 8800 and try that for giggles.

        Because of the noisy buss, put all RAM as physically close as
        possible to the CPU board.

        [ESK] I've got three 4-slot motherboards in the 8800. The first contains the processor, the PROM board and a 32K SRAM card, the next has the SIO-2, 16K and 8K Static cards the last has the 2 drive controllers.

        The code in those old 1702 EPROMs can become corrupted after almost
        30 years. Try using the apparently good boot PROM from the BT in the
        8800. If you're using chips that you bought from altairmanuals.com,
        they should still be good for a long time to come unless you remove
        the sticker from the erasure window.

        [ESK] I've done both. I have new PROMS from Altairmanuals.com and I've moved the 4.1 PROM from the BT to the 8800. All PROMs have worked about the same.

        Even if you do have a bad serial I/O board for your terminal, you
        should still see the disk's head stepping from track to track as it
        boots. The boot ROM doesn't check for the presence of a terminal or
        even an I/O board like modern PCs do. Since the head doesn't move
        after loading, I think the problem is not the serial board.

        [ESK] I'm inclined to agree. I'm not sure if the heads move more then one track before prompting on the 8800BT, but I can take the cover off and watch both machines try to boot to be sure.

        [ESK] I'll post progress when I make any (I may not have time to try these things for a while).

        [ESK] If y'all get any other ideas, please let me know!

        Thanks!

        Erik



        Steve
        =========================

        --- In altaircomputerclub@yahoogroups.com, ErikSKlein <no_reply@y...>
        wrote:
        > Hello all,
        >
        > I just found this group while poking away at the net. I'm glad
        > there's a community of Altair users/collectors. . .
        >
        > First off, I have a Vintage Computer Collecting forum that I
        started
        > as an extension of my website at www.vintage-computer.com/vcforum.
        > It has been accessible for about a week now and we've already got
        > over 120 posts. I'm hoping that by getting the word out we can
        > create a dynamic community.
        >
        > I encourage you to head over and take a look.
        >
        > Now, my question:
        >
        > As part of my collection I have an Altair 8800 (actually 2, but one
        > is being rebuilt) and an Altair 8800BT.
        >
        > The 8800BT came with a pair of MITS 8" drives (Pertec drive, MITS
        > controller in the drives and machine) and it works perfectly. Turn
        > the key and the machine boots to a prompt.
        >
        > The 8800 came with the same setup but never booted. I recently
        tried
        > a few things to figure out where the problem was.
        >
        > First of all, I tested the 8800 set of disk controller boards in
        the
        > working 8800bt system and I have and determined that the cards are
        > not the problem. (The drives that came with the 8800 aren't quite
        > functional, but they are close)
        >
        > I then returned my attention to the original 8800 with its
        > controller cards hooked up to the pair of known-good drives. For
        the
        > life of me I can't get this machine to function properly. I have no
        > idea why it won't boot, but it won't. It goes through the motions;
        > it enables the boot drive and loads the heads but it won't output
        > anything to the terminal.
        >
        > I suspected the serial card until I ran a test on that and was able
        > to get it to spit data out from the proper output port. I've tested
        > every other aspect of the system, within reason, and the machine
        > appears to be fine. It just won't cooperate with me about booting.
        > I'm at my wits end trying to boot this machine.
        >
        > Does anyone have any suggestions about what I can try next? I'd
        > really like to have the 8800 boot from the drives someday. . .
        >
        > Erik



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      • akessel
        Here is your problem ... at 177000 so I turn the machine on, raise stop and reset simultaneously, raise the first 8 switches (A15-A8) and raise Examine. I
        Message 3 of 11 , May 6, 2003
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          Here is your problem

          > [ESK] I am directly addressing the boot prom. I'm pretty sure it's
          at 177000 so I turn the machine on, raise stop and reset
          simultaneously, raise the first 8 switches (A15-A8) and raise
          Examine. I then "run."

          Raise the switches, examine, put all switches down and then run.
        • Erik S. Klein
          I ve done that and I ve tried other variations based on the sense switch settings indicated in the Altair BASIC manual - even the ones that had nothing to do
          Message 4 of 11 , May 6, 2003
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            I've done that and I've tried other variations based on the sense switch
            settings indicated in the Altair BASIC manual - even the ones that had
            nothing to do with my configuration.



            I just tried it again now and got the same result - the Altair talks to
            the drive, the drive enables the disk and loads the heads and then stops
            with no data showing on the terminal.



            Erik



            -----Original Message-----
            From: akessel [mailto:no_reply@yahoogroups.com]
            Sent: Tuesday, May 06, 2003 3:26 PM
            To: altaircomputerclub@yahoogroups.com
            Subject: [Altair Computer Club] Re: New Vintage Computer Forum and a
            question



            Here is your problem

            > [ESK] I am directly addressing the boot prom. I'm pretty sure it's
            at 177000 so I turn the machine on, raise stop and reset
            simultaneously, raise the first 8 switches (A15-A8) and raise
            Examine. I then "run."

            Raise the switches, examine, put all switches down and then run.









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          • alltare
            Erik, You re lucky to have two machines to compare, even if they aren t the same models. Troubleshooting is a lot tougher with just one computer. I think
            Message 5 of 11 , May 6, 2003
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              Erik,

              You're lucky to have two machines to compare, even if they aren't the
              same models. Troubleshooting is a lot tougher with just one computer.

              I think you're examining the correct starting address of the DBL boot
              ROM, but you mistyped it in your answer. The correct address to
              examine then run is 177400 or hex FF00. You said 177000, which is
              the address of the MBL cassette loader. You were correct, though,
              when you said you raised the 8 switches for A15 thru A8.

              Are you using the same good I/O cable (the ribbon cable that goes
              from the computer to the drives) with both computers? It's not
              unheard of to have bad connections in them.

              You know the CPU board, PROM board, and DBL are all probably good or
              you wouldn't be getting the head to load on the floppy. On the other
              hand, the problem you're having can indicate bad RAM.

              I would try to eliminate as many variables as possible. That is, use
              the same known good RAM boards, controllers, cables, drives, drive
              interfaces, diskettes, etc. in both machines. You can't use the BT's
              Turnkey board, serial port (you're using the one on the turnkey
              board, I assume), or CPU board, but the other boards should be OK in
              either machine.

              Have you checked the 3 system voltages on the 8800? Sometimes it was
              easy to overload the 8800's -12V supply (the raw DC should be
              about -16V on the buss and where it enters boards' -12V regulation
              circuits). The supplies on the model B were relatively bulletproof.

              Be sure none of the fragile wires going from the mother board to the
              front panel have broken loose at either end.

              PS to akessel- You should be able to leave or put the address
              switches in any position after you have examined the correct starting
              address of the boot ROM (177400). You shouldn't need to flip them
              all down before hitting the RUN switch. Andy, are you sure your
              computer really require all switches to be down before running?

              By the way, Erik's method of raising STOP and RESET together is a
              good one. Sometimes, but not always, the 8800/8800A would
              get "stuck" and you couldn't stop or reset it to 0000 with just one
              switch. The 2-switch method was the recommended action.

              steve
              ============================

              --- In altaircomputerclub@yahoogroups.com, Erik Klein <Lifo@p...>
              wrote:
              > I've inserted my responses below. Hopefully the formatting isn't
              too screwy.
              >
              > alltare <no_reply@yahoogroups.com> wrote:
              > Erik,
              >
              > These questions/comments come to mind:
              >
              > How are you booting the 8800? Are you directly addressing and
              > executing the boot PROM, using a turnkey board with Turmon PROM, or
              > what?
              >
              > [ESK] I am directly addressing the boot prom. I'm pretty sure it's
              at 177000 so I turn the machine on, raise stop and reset
              simultaneously, raise the first 8 switches (A15-A8) and raise
              Examine. I then "run."
              >
              > [ESK] I've tried several variations of sense switch settings with
              the above (set after examine, before I run)
              >
              > What boot PROM are you using (DBL, MDBL, ...)?
              >
              > [ESK] I am using a DBL PROM. I have at least two versions of this,
              one of which seems to match up to the 4.1 version in the 8800BT I
              have.
              >
              > MITS had two 8" disk "formats"- the original and the later "NWD"
              (New
              > Write Delay) format. There were several timing changes to the
              > controller boards and therefore to the recorded data. I think you
              > have a paper giving the various timing differences. You may be
              using
              > relatively incompatible controller/diskette combinations that
              totally
              > fail to work right in the 8800. I think all model B's were
              supplied
              > with NWD controllers, and almost all 8800s had controllers with the
              > original pre-NWD timing.
              >
              > [ESK] I have two sets of functional controllers between the 8800
              and the 8800BT. Both work on the drives and disk as attached to the
              8800BT, neither works on the 8800.
              >
              > How much RAM is in the 8800? Are you sure all RAM is good? You
              > should probably have at least 32K of good memory (beginning at
              > address 0) to load later versions of BASIC. Try readdressing your
              > RAM boards or swapping with those known good ones from the 8800BT.
              > On MITS' 16K boards, they had real problems with the 4-position DIP
              > switches used for addressing (dirty contacts with resistance of a
              few
              > ohms)- often the switches would be replaced with soldered jumpers
              as
              > a cure. Try restricting max RAM to no more than 48K.
              >
              > [ESK] I've got anywhere between 32 and 56K in the machine at any
              time when I've been doing testing. I'm pretty sure that all of the
              RAM is good although I haven't tested every bit. I may swap over the
              3 16MCDs from the BT to the 8800 and try that for giggles.
              >
              > Because of the noisy buss, put all RAM as physically close as
              > possible to the CPU board.
              >
              > [ESK] I've got three 4-slot motherboards in the 8800. The first
              contains the processor, the PROM board and a 32K SRAM card, the next
              has the SIO-2, 16K and 8K Static cards the last has the 2 drive
              controllers.
              >
              > The code in those old 1702 EPROMs can become corrupted after almost
              > 30 years. Try using the apparently good boot PROM from the BT in
              the
              > 8800. If you're using chips that you bought from
              altairmanuals.com,
              > they should still be good for a long time to come unless you remove
              > the sticker from the erasure window.
              >
              > [ESK] I've done both. I have new PROMS from Altairmanuals.com and
              I've moved the 4.1 PROM from the BT to the 8800. All PROMs have
              worked about the same.
              >
              > Even if you do have a bad serial I/O board for your terminal, you
              > should still see the disk's head stepping from track to track as it
              > boots. The boot ROM doesn't check for the presence of a terminal
              or
              > even an I/O board like modern PCs do. Since the head doesn't move
              > after loading, I think the problem is not the serial board.
              >
              > [ESK] I'm inclined to agree. I'm not sure if the heads move more
              then one track before prompting on the 8800BT, but I can take the
              cover off and watch both machines try to boot to be sure.
              >
              > [ESK] I'll post progress when I make any (I may not have time to
              try these things for a while).
              >
              > [ESK] If y'all get any other ideas, please let me know!
              >
              > Thanks!
              >
              > Erik
              >
              > (snip)
            • Erik S. Klein
              ... I m certainly having an easier time troubleshooting now that I have a known-good configuration. I ve had my 8800 and 8800a with their drives for about a
              Message 6 of 11 , May 6, 2003
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                > You're lucky to have two machines to compare, even if they aren't the
                > same models. Troubleshooting is a lot tougher with just one computer.



                I'm certainly having an easier time troubleshooting now that I have a
                known-good configuration. I've had my 8800 and 8800a with their drives
                for about a year and a half but just got the BT and its drives a few
                months ago. When that machine booted up out of the box I was ecstatic
                because I knew I'd have my other machines figured out eventually.

                > I think you're examining the correct starting address of the DBL boot
                > ROM, but you mistyped it in your answer. The correct address to
                > examine then run is 177400 or hex FF00. You said 177000, which is
                > the address of the MBL cassette loader. You were correct, though,
                > when you said you raised the 8 switches for A15 thru A8.



                Yeah, I was trying to do Octal in my head to get the email out before a
                meeting. . . :-)



                If the 177400 address is for the MBL then I can have both mounted at the
                same time. I figured the MBL was set up for another address but I
                hadn't gone so far as to figure out what that was. . Thanks!


                > Are you using the same good I/O cable (the ribbon cable that goes
                > from the computer to the drives) with both computers? It's not
                > unheard of to have bad connections in them.



                I am using the same ribbon cable. I've got a bunch around, of course,
                with one for each drive. The cable within the machine from the disk
                boards to the connector in the back might be in question, but it seemed
                okay on physical examination. I may have to pull out the manual and
                meter and make sure it's pinned right and that there is connectivity
                where there should be.


                > You know the CPU board, PROM board, and DBL are all probably good or
                > you wouldn't be getting the head to load on the floppy. On the other
                > hand, the problem you're having can indicate bad RAM.



                Yeah. Swapping the 8800BT RAM in is a good idea. I'll have to do that
                soon. I should also find or write a quick RAM test program (I'm pretty
                sure there are some small ones in the older magazines like Byte or Dr.
                Dobb's. I have plugged in some reasonable code via the front panel, but
                never more then a few hundred bytes.

                > I would try to eliminate as many variables as possible. That is, use
                > the same known good RAM boards, controllers, cables, drives, drive
                > interfaces, diskettes, etc. in both machines. You can't use the BT's
                > Turnkey board, serial port (you're using the one on the turnkey
                > board, I assume), or CPU board, but the other boards should be OK in
                > either machine.



                Yep. I've done it all but the RAM including the boot PROM from the BT.


                > Have you checked the 3 system voltages on the 8800? Sometimes it was
                > easy to overload the 8800's -12V supply (the raw DC should be
                > about -16V on the buss and where it enters boards' -12V regulation
                > circuits). The supplies on the model B were relatively bulletproof.



                I've done that periodically while diagnosing other problems. I don't
                know if I've checked with the system fully loaded in the current
                configuration. When I swap in the RAM that's an easy test to perform so
                I'll do it then.


                > Be sure none of the fragile wires going from the mother board to the
                > front panel have broken loose at either end.



                I am quite certain that the internal wiring is 100%. I've tested every
                wire to the front panel, power supply, processor and motherboard and
                I've tested every pin on the buss for continuity. I'm confident that
                the problem wouldn't lie there. By the way, what type (solid or
                braided) and gauge of wire is used for those front panel lines? I need
                to rewire another Altair and I want to use something as close to
                authentic as possible.


                > PS to akessel- You should be able to leave or put the address
                > switches in any position after you have examined the correct starting
                > address of the boot ROM (177400). You shouldn't need to flip them
                > all down before hitting the RUN switch. Andy, are you sure your
                > computer really require all switches to be down before running?



                Actually, I think this depends on WHAT you're running. Disk BASIC
                requires "Sense Switches" to be set to indicate what communications
                device and parameters are to be used. These are the upper 8 address
                switches (as indicated by the silk screening on the front panel) and the
                configurations are part of the BASIC manual. I've tried all of the
                variations. The BT has a dip switch block dedicated to the sense
                switches.


                > By the way, Erik's method of raising STOP and RESET together is a
                > good one. Sometimes, but not always, the 8800/8800A would
                > get "stuck" and you couldn't stop or reset it to 0000 with just one
                > switch. The 2-switch method was the recommended action.



                I do want to thank you guys for all of your help and all of your
                insightful, knowledgeable responses. Like I said in my first email, I
                stumbled across this list by accident and I've gotten more information
                about this problem here then I have on any other forums or lists in the
                past year. This is the type of exchange I am hoping to get out of my
                web forum someday soon. . .



                Best regards,


                Erik

                www.vintage-computer.com <http://www.vintage-computer.com/>





                [Non-text portions of this message have been removed]
              • akessel
                One other suggestion if you want to test things and you have the mbl prom. I have binarys of the extended disk basic you can upload to the 8800 using the mbl
                Message 7 of 11 , May 6, 2003
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                  One other suggestion if you want to test things and you have the mbl
                  prom. I have binarys of the extended disk basic you can upload to
                  the 8800 using the mbl instructions at:
                  http://www.altairage.com/languages/Basic%20Instructions.htm

                  you will need a program to do a serial binary upload, and I mention a
                  few in the article - why don't you see if you can get disk basic or
                  one of the other basics to load and run, then you can at least make
                  sure that the problem is somewhere on the disk loading side.

                  All my Altair issues have been either RAM, Cables or a board
                  problem. Anyway, you need to eliminate possible issues. Good luck.

                  PS what steve doesn't know, I'm not sure anyone else knows. My info
                  is from writing down what worked after fussing with steve for
                  months. Its been fun and a challenge.

                  Andy
                • alltare
                  Erik, Yes, the MBL and DBL/MDBL can be on your 2K PROM board or turnkey board at the same time. Just jump to or examine one or the other starting address as
                  Message 8 of 11 , May 7, 2003
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                    Erik,

                    Yes, the MBL and DBL/MDBL can be on your 2K PROM board or turnkey
                    board at the same time. Just jump to or examine one or the other
                    starting address as desired. You made another typo in your latest
                    message, so let me clarify where the EPROMs go:
                    DBL or MDBL (Disk or Mini Disk Boot Loader) goes at 177400 or hex
                    FF00.
                    MBL (Multi Boot Loader- for paper tape & cassette) goes at
                    177000/FE00.
                    TURMON (TURnkey MONitor) goes at 176400/FD00 on the turnkey board.

                    I got so used to using a turnkey board way back then that I forgot
                    about the sense switch settings, so I guess I was wrong about how to
                    set the address switches when booting. Andy has played around with
                    these things a lot, so he's the expert. He's also put a lot of hard
                    work into understanding boot ROMs and doing dumps of the OPSYS.

                    I'm still thinking that you have a memory problem of some kind. I
                    guess you might make sure that each board is properly addressed, that
                    no two boards occupy the same memory address, and that there are no
                    gaps in memory.

                    The best RAM boards by MITS were their 16MCS 16K statics. Use those
                    if you have any. There were problems with them, though. Besides the
                    4-position DIP switch having bad contacts, the memory chips would
                    often tend to vibrate out of their sockets and have bad connections.
                    Lay the boards on a flat surface and manually press each chip back
                    into place. This was only a real problem with the 16K statics. If
                    you havent ever done this, you're sure to find several chips on each
                    board that aren't fully seated.

                    I'm running out of ideas, and you've already thought of everything I
                    said anyway. I'll sure like to know what the problem is once you
                    figure it out.

                    Steve
                    ==========================


                    --- In altaircomputerclub@yahoogroups.com, "Erik S. Klein"
                    <Lifo@p...> wrote:
                    > > You're lucky to have two machines to compare, even if they aren't
                    the
                    > > same models. Troubleshooting is a lot tougher with just one
                    computer.
                    >
                    >
                    >
                    > I'm certainly having an easier time troubleshooting now that I have
                    a
                    > known-good configuration. I've had my 8800 and 8800a with their
                    drives
                    > for about a year and a half but just got the BT and its drives a few
                    > months ago. When that machine booted up out of the box I was
                    ecstatic
                    > because I knew I'd have my other machines figured out eventually.
                    >
                    > > I think you're examining the correct starting address of the DBL
                    boot
                    > > ROM, but you mistyped it in your answer. The correct address to
                    > > examine then run is 177400 or hex FF00. You said 177000, which
                    is
                    > > the address of the MBL cassette loader. You were correct,
                    though,
                    > > when you said you raised the 8 switches for A15 thru A8.
                    >
                    >
                    >
                    > Yeah, I was trying to do Octal in my head to get the email out
                    before a
                    > meeting. . . :-)
                    >
                    >
                    >
                    > If the 177400 address is for the MBL then I can have both mounted
                    at the
                    > same time. I figured the MBL was set up for another address but I
                    > hadn't gone so far as to figure out what that was. . Thanks!
                    >
                    >
                    > > Are you using the same good I/O cable (the ribbon cable that goes
                    > > from the computer to the drives) with both computers? It's not
                    > > unheard of to have bad connections in them.
                    >
                    >
                    >
                    > I am using the same ribbon cable. I've got a bunch around, of
                    course,
                    > with one for each drive. The cable within the machine from the disk
                    > boards to the connector in the back might be in question, but it
                    seemed
                    > okay on physical examination. I may have to pull out the manual and
                    > meter and make sure it's pinned right and that there is connectivity
                    > where there should be.
                    >
                    >
                    > > You know the CPU board, PROM board, and DBL are all probably good
                    or
                    > > you wouldn't be getting the head to load on the floppy. On the
                    other
                    > > hand, the problem you're having can indicate bad RAM.
                    >
                    >
                    >
                    > Yeah. Swapping the 8800BT RAM in is a good idea. I'll have to do
                    that
                    > soon. I should also find or write a quick RAM test program (I'm
                    pretty
                    > sure there are some small ones in the older magazines like Byte or
                    Dr.
                    > Dobb's. I have plugged in some reasonable code via the front
                    panel, but
                    > never more then a few hundred bytes.
                    >
                    > > I would try to eliminate as many variables as possible. That is,
                    use
                    > > the same known good RAM boards, controllers, cables, drives,
                    drive
                    > > interfaces, diskettes, etc. in both machines. You can't use the
                    BT's
                    > > Turnkey board, serial port (you're using the one on the turnkey
                    > > board, I assume), or CPU board, but the other boards should be OK
                    in
                    > > either machine.
                    >
                    >
                    >
                    > Yep. I've done it all but the RAM including the boot PROM from the
                    BT.
                    >
                    >
                    > > Have you checked the 3 system voltages on the 8800? Sometimes it
                    was
                    > > easy to overload the 8800's -12V supply (the raw DC should be
                    > > about -16V on the buss and where it enters boards' -12V
                    regulation
                    > > circuits). The supplies on the model B were relatively
                    bulletproof.
                    >
                    >
                    >
                    > I've done that periodically while diagnosing other problems. I
                    don't
                    > know if I've checked with the system fully loaded in the current
                    > configuration. When I swap in the RAM that's an easy test to
                    perform so
                    > I'll do it then.
                    >
                    >
                    > > Be sure none of the fragile wires going from the mother board to
                    the
                    > > front panel have broken loose at either end.
                    >
                    >
                    >
                    > I am quite certain that the internal wiring is 100%. I've tested
                    every
                    > wire to the front panel, power supply, processor and motherboard and
                    > I've tested every pin on the buss for continuity. I'm confident
                    that
                    > the problem wouldn't lie there. By the way, what type (solid or
                    > braided) and gauge of wire is used for those front panel lines? I
                    need
                    > to rewire another Altair and I want to use something as close to
                    > authentic as possible.
                    >
                    >
                    > > PS to akessel- You should be able to leave or put the address
                    > > switches in any position after you have examined the correct
                    starting
                    > > address of the boot ROM (177400). You shouldn't need to flip
                    them
                    > > all down before hitting the RUN switch. Andy, are you sure your
                    > > computer really require all switches to be down before running?
                    >
                    >
                    >
                    > Actually, I think this depends on WHAT you're running. Disk BASIC
                    > requires "Sense Switches" to be set to indicate what communications
                    > device and parameters are to be used. These are the upper 8 address
                    > switches (as indicated by the silk screening on the front panel)
                    and the
                    > configurations are part of the BASIC manual. I've tried all of the
                    > variations. The BT has a dip switch block dedicated to the sense
                    > switches.
                    >
                    >
                    > > By the way, Erik's method of raising STOP and RESET together is a
                    > > good one. Sometimes, but not always, the 8800/8800A would
                    > > get "stuck" and you couldn't stop or reset it to 0000 with just
                    one
                    > > switch. The 2-switch method was the recommended action.
                    >
                    >
                    >
                    > I do want to thank you guys for all of your help and all of your
                    > insightful, knowledgeable responses. Like I said in my first
                    email, I
                    > stumbled across this list by accident and I've gotten more
                    information
                    > about this problem here then I have on any other forums or lists in
                    the
                    > past year. This is the type of exchange I am hoping to get out of
                    my
                    > web forum someday soon. . .
                    >
                    >
                    >
                    > Best regards,
                    >
                    >
                    > Erik
                    >
                    > www.vintage-computer.com <http://www.vintage-computer.com/>
                    >
                    >
                    >
                    >
                    >
                    > [Non-text portions of this message have been removed]
                  • Erik S. Klein
                    ... That’s good information. I’ll have to do some playing with the MBL and serial uploads from my PC emulating a tape or paper tape device. ... As it
                    Message 9 of 11 , May 14, 2003
                    • 0 Attachment
                      --- In altaircomputerclub@yahoogroups.com, Steve wrote:

                      >Yes, the MBL and DBL/MDBL can be on your 2K PROM board or turnkey
                      >board at the same time.  Just jump to or examine one or the other
                      >starting address as desired.  You made another typo in your latest
                      >message, so let me clarify where the EPROMs go:
                      >DBL or MDBL (Disk or Mini Disk Boot Loader) goes at 177400 or hex
                      >FF00.
                      >MBL (Multi Boot Loader- for paper tape & cassette) goes at
                      >177000/FE00.
                      >TURMON (TURnkey MONitor) goes at 176400/FD00 on the turnkey board.

                      That’s good information. I’ll have to do some playing with the MBL and
                      serial uploads from my PC emulating a tape or paper tape device.

                      >I'm still thinking that you have a memory problem of some kind.  I
                      >guess you might make sure that each board is properly addressed, that
                      >no two boards occupy the same memory address, and that there are no
                      >gaps in memory.

                      As it turns out, this is exactly right. I swapped over the 16MCDs from
                      the 8800BT to the 8800 and it booted like a champ.

                      Now I have to figure out what about my 56K (1x32, 1x16, 1x8) in the 8800
                      is bad. I am pretty sure everything is addressed properly and I know
                      that I have been able to read and write bits correctly on all of the
                      boards.

                      >The best RAM boards by MITS were their 16MCS 16K statics.  Use those
                      >if you have any.  There were problems with them, though.  Besides the
                      >4-position DIP switch having bad contacts, the memory chips would
                      >often tend to vibrate out of their sockets and have bad connections. 
                      >Lay the boards on a flat surface and manually press each chip back
                      >into place.  This was only a real problem with the 16K statics.  If
                      >you havent ever done this, you're sure to find several chips on each
                      >board that aren't fully seated.

                      The 16K board is a 16MCS, the 32K is from Artech and the 8K is a Seals.
                      I’ll re-check all of the settings and whatever else I think of when I
                      next get free time.

                      Thanks!

                      Erik
                      www.vintage-computer.com
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