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Cosmac VIP recreation

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  • dougjacksondrj113
    Hello to the group, I have recently obtained a couple of 1861 graphics chips thasnks to a fellow ELF enthusiast, and I have decided to construct a reproduction
    Message 1 of 9 , Oct 5, 2008
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      Hello to the group,

      I have recently obtained a couple of 1861 graphics chips thasnks to a
      fellow ELF enthusiast, and I have decided to construct a reproduction
      of the VIP. I have captured the schematic from the VIP users manual
      that I found in this forum.

      I have taken care to replace tricky to obtain components wherever
      possible with modern equivalents (except, of course the CPU and PIXIE
      chip). This is especially noticable in the memory and I/O areas.
      Where possible, I have also simplified the decoding. My benchmark is
      the local Jaycar catalogue. My goal is to re-create the VIP, not
      totally re-engineer it down to a couple of parts. I still want
      something about A4 in size. This version has 2K of ROM, and 8K of
      RAM. I should be easilly able to include CHIP-8 in the new ROM, so it
      is copied into ram on startup, removing the need to type in CHIP-8.

      I would appreciate it if somebody could cast their eyes over the new
      diagrams in case I have lost the plot - Actually, my loving wife
      thinks that I am mad, but at least it is something I can focus on.

      I will be laying out a new board in the next couple of weeks. At
      home, I have single sided production facilities, so the board will be
      single sided with top side jumpers. In case anybody is interested, I
      am using the software provided by Express PCB, as it does not have
      size limitations, is free, and is trivial to use.
    • Doug Jackson
      Hi again I was wondering if anybody here knew what the pin pitch was on the expansion and I/O connector on the VIP. It is important to me that expansion cards
      Message 2 of 9 , Oct 9, 2008
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        Hi again

        I was wondering if anybody here knew what the pin pitch was on the
        expansion and I/O connector on the VIP. It is important to me that
        expansion cards operate correctly!

        Next, could somebody actually measure their VIP - I have the dimensions
        from a brochure, but nothing beats actually using a ruler. Also, if
        anybody has a reasonable recolution scan of the top of the board, so I
        can get the component spacing correct, it would be appreciated. As I
        mentioned in my original email, my goal is to recreate closely, but with
        more easy to obtain components.

        Finally, in spite of the above question, it looks like the costs can be
        reduced *significantly* if the recreation were made smaller. Given the
        low component density, what do people feel about reducing the size
        accordingly - probably to approximately A5 in size (approx 8"x6").

        Thanks,

        Doug
      • Ray Sills
        HI Doug: Those connectors are 44 pin Blue Ribbon connectors. I did find some Google listings about the connectors, but no detailed listings about the pin
        Message 3 of 9 , Oct 9, 2008
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          HI Doug:

          Those connectors are 44 pin "Blue Ribbon" connectors. I did find some
          Google listings about the connectors, but no detailed listings about
          the pin spacing. I don't have a metric ruler handy, so I can't give
          proper measurements. The base is 4 1/2 inches long (where it rests on
          the circuit board). The "shoulders" are 1/4" each, so that top part
          where the connector pins are is 3 3/4" wide. The spacing from the
          left most edge of the first set of edge pins to the left most edge of
          the 22nd edge pin is 3 9/32".. so I suspect the spacings are metric.
          That measurement is subject to the accuracy of my eyes and the steel
          tape ruler I used. It's about 83+ mm. If it were 88 mm... dividing
          that by 22 (number of pins on each row).. would be 4 mm spacing. So,
          it may be close to that.

          There's a lot of "slack' in the spacing, since there is as much space
          between pins as the pins are wide.. probably to allow for
          manufacturing variations. I don't think it should be too critical.
          The slot to hold the board edge is 4 5/8" so a board with 4 1/2" width
          would slide in easily, but not be so far off to mis-align with the
          connector pins.

          On disadvantage of the Blue Ribbon connectors as used on the VIP is
          that they are not keyed in any way... so you could stick a board in
          backwards.
          As I recall with the VIP, any board inserted into the expansion ports
          should have the top (where the chips are) facing the front of the VIP.

          I recently fired up one of my old VIPs... and am pleased to report
          that it's working fine. I had some trouble loading old tapes, but
          managed to find a tape and tape machine that still were OK. It's been
          decades since I last loaded in those tapes, so I bet most have
          deteriorated to being unusable.

          73 de Ray


          On Oct 9, 2008, at 3:46 PM, Doug Jackson wrote:

          > Hi again
          >
          > I was wondering if anybody here knew what the pin pitch was on the
          > expansion and I/O connector on the VIP. It is important to me that
          > expansion cards operate correctly!
          >
          > Next, could somebody actually measure their VIP - I have the
          > dimensions
          > from a brochure, but nothing beats actually using a ruler. Also, if
          > anybody has a reasonable recolution scan of the top of the board, so I
          > can get the component spacing correct, it would be appreciated. As I
          > mentioned in my original email, my goal is to recreate closely, but
          > with
          > more easy to obtain components.
          >
          > Finally, in spite of the above question, it looks like the costs can
          > be
          > reduced *significantly* if the recreation were made smaller. Given
          > the
          > low component density, what do people feel about reducing the size
          > accordingly - probably to approximately A5 in size (approx 8"x6").
          >
          > Thanks,
          >
          > Doug
          >
          >
          >
          > ------------------------------------
          >
          > Yahoo! Groups Links
          >
          >
          >
        • Ray Sills
          Replying to my own message: Error check: The measurements in the 2nd paragraph should be 3 inches plus whatever... not 4. (I forgot I was using the 1 point as
          Message 4 of 9 , Oct 9, 2008
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            Replying to my own message:

            Error check:

            The measurements in the 2nd paragraph should be 3 inches plus
            whatever... not 4.

            (I forgot I was using the 1" point as the start). :o )

            73 de Ray


            On Oct 9, 2008, at 8:06 PM, Ray Sills wrote:

            > HI Doug:
            >
            > Those connectors are 44 pin "Blue Ribbon" connectors. I did find some
            > Google listings about the connectors, but no detailed listings about
            > the pin spacing. I don't have a metric ruler handy, so I can't give
            > proper measurements. The base is 4 1/2 inches long (where it rests on
            > the circuit board). The "shoulders" are 1/4" each, so that top part
            > where the connector pins are is 3 3/4" wide. The spacing from the
            > left most edge of the first set of edge pins to the left most edge of
            > the 22nd edge pin is 3 9/32".. so I suspect the spacings are metric.
            > That measurement is subject to the accuracy of my eyes and the steel
            > tape ruler I used. It's about 83+ mm. If it were 88 mm... dividing
            > that by 22 (number of pins on each row).. would be 4 mm spacing. So,
            > it may be close to that.
            >
            > There's a lot of "slack' in the spacing, since there is as much space
            > between pins as the pins are wide.. probably to allow for
            > manufacturing variations. I don't think it should be too critical.
            > The slot to hold the board edge is 4 5/8" so a board with 4 1/2" width
            > would slide in easily, but not be so far off to mis-align with the
            > connector pins.
            >
            > On disadvantage of the Blue Ribbon connectors as used on the VIP is
            > that they are not keyed in any way... so you could stick a board in
            > backwards.
            > As I recall with the VIP, any board inserted into the expansion ports
            > should have the top (where the chips are) facing the front of the VIP.
            >
            > I recently fired up one of my old VIPs... and am pleased to report
            > that it's working fine. I had some trouble loading old tapes, but
            > managed to find a tape and tape machine that still were OK. It's been
            > decades since I last loaded in those tapes, so I bet most have
            > deteriorated to being unusable.
            >
            > 73 de Ray
            >
            >
            > On Oct 9, 2008, at 3:46 PM, Doug Jackson wrote:
            >
            >> Hi again
            >>
            >> I was wondering if anybody here knew what the pin pitch was on the
            >> expansion and I/O connector on the VIP. It is important to me that
            >> expansion cards operate correctly!
            >>
            >> Next, could somebody actually measure their VIP - I have the
            >> dimensions
            >> from a brochure, but nothing beats actually using a ruler. Also, if
            >> anybody has a reasonable recolution scan of the top of the board,
            >> so I
            >> can get the component spacing correct, it would be appreciated. As I
            >> mentioned in my original email, my goal is to recreate closely, but
            >> with
            >> more easy to obtain components.
            >>
            >> Finally, in spite of the above question, it looks like the costs can
            >> be
            >> reduced *significantly* if the recreation were made smaller. Given
            >> the
            >> low component density, what do people feel about reducing the size
            >> accordingly - probably to approximately A5 in size (approx 8"x6").
            >>
            >> Thanks,
            >>
            >> Doug
            >>
            >>
            >>
            >> ------------------------------------
            >>
            >> Yahoo! Groups Links
            >>
            >>
            >>
            >
            >
            > ------------------------------------
            >
            > Yahoo! Groups Links
            >
            >
            >
          • erd_6502
            ... Hi, Doug, Those are standard (and once very common) 44/22-pin, 0.156 -spacing connectors (for the record, 4mm is a close measurement, but not quite close
            Message 5 of 9 , Oct 9, 2008
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              --- In rcacosmac@yahoogroups.com, Doug Jackson <doug@...> wrote:
              >
              > Hi again
              >
              > I was wondering if anybody here knew what the pin pitch was on the
              > expansion and I/O connector on the VIP. It is important to me that
              > expansion cards operate correctly!

              Hi, Doug,

              Those are standard (and once very common) 44/22-pin,
              0.156"-spacing connectors (for the record, 4mm is a
              close measurement, but not quite close enough for
              layout - it's really 3.96mm, give or take).

              These connectors were once so common, you could buy matching
              prototype boards at Radio Shack. It's even the cartridge
              connector for a Commodore VIC-20.

              > Next, could somebody actually measure their VIP

              I would, but mine is thousands of miles from me right now.

              > Finally, in spite of the above question, it looks like the
              > costs can be reduced *significantly* if the recreation were
              > made smaller.

              Naturally. That's one large board by today's standards. I
              have a replica KIM-1 that's probably 25% of the size of the
              original, and no edge connectors (if you don't know what
              a KIM-1 looks like, if the spacing between its connectors
              was right, it could almost plug into both slots of a VIP
              at once). The replica just has a modernish 40-pin 0.1"
              connector - like the kind used for an IDE disk. Much like
              the VIP, though, the KIM-1 had one connector for I/O
              and one for memory expansion. The replica only has the
              memory expansion signals, and left the I/O expansion for
              off-board.

              > Given the
              > low component density, what do people feel about reducing the size
              > accordingly - probably to approximately A5 in size (approx 8"x6").

              That's still pretty large. Is that to make room for the
              two 44-pin AMP connectors?

              What were you planning on doing for a keypad? Individual
              pushbutton switches? I wouldn't know where one could get
              a suitable membrane keypad these days.

              -ethan
            • Doug Jackson
              Hi Ethan, the places you see people - I normally see you in cctalk!... Keypad - yep - standard modern tactile switches, as used in just about every VCR on the
              Message 6 of 9 , Oct 10, 2008
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                Hi Ethan,

                the places you see people - I normally see you in cctalk!...

                Keypad - yep - standard modern tactile switches, as used in just about
                every VCR on the planet - advantage, cheap as chips...

                Size - The initial estimate of A5 was to make sure that the edge
                connectors could be used - That also makes space for the hex keypad. I
                also have a bucked load of PCB stock here that is about that size - so
                my prototype can be made with simple facilities, and top-side links.

                Thanks for your help on the edge connector front - They were very common
                - I suspect I have a couple in my junk box(es) here.

                Take care, and enjoy the penguins

                Doug

                erd_6502 wrote:
                >
                > --- In rcacosmac@yahoogroups.com <mailto:rcacosmac%40yahoogroups.com>,
                > Doug Jackson <doug@...> wrote:
                > >
                > > Hi again
                > >
                > > I was wondering if anybody here knew what the pin pitch was on the
                > > expansion and I/O connector on the VIP. It is important to me that
                > > expansion cards operate correctly!
                >
                > Hi, Doug,
                >
                > Those are standard (and once very common) 44/22-pin,
                > 0.156"-spacing connectors (for the record, 4mm is a
                > close measurement, but not quite close enough for
                > layout - it's really 3.96mm, give or take).
                >
                > These connectors were once so common, you could buy matching
                > prototype boards at Radio Shack. It's even the cartridge
                > connector for a Commodore VIC-20.
                >
                > > Next, could somebody actually measure their VIP
                >
                > I would, but mine is thousands of miles from me right now.
                >
                > > Finally, in spite of the above question, it looks like the
                > > costs can be reduced *significantly* if the recreation were
                > > made smaller.
                >
                > Naturally. That's one large board by today's standards. I
                > have a replica KIM-1 that's probably 25% of the size of the
                > original, and no edge connectors (if you don't know what
                > a KIM-1 looks like, if the spacing between its connectors
                > was right, it could almost plug into both slots of a VIP
                > at once). The replica just has a modernish 40-pin 0.1"
                > connector - like the kind used for an IDE disk. Much like
                > the VIP, though, the KIM-1 had one connector for I/O
                > and one for memory expansion. The replica only has the
                > memory expansion signals, and left the I/O expansion for
                > off-board.
                >
                > > Given the
                > > low component density, what do people feel about reducing the size
                > > accordingly - probably to approximately A5 in size (approx 8"x6").
                >
                > That's still pretty large. Is that to make room for the
                > two 44-pin AMP connectors?
                >
                > What were you planning on doing for a keypad? Individual
                > pushbutton switches? I wouldn't know where one could get
                > a suitable membrane keypad these days.
                >
                > -ethan
                >
                >
              • ddmaow
                Power and ground are transposed on the byte interface? Might be good to buffer Q there if possible. Why not use a larger EPROM? 2716 s are getting rare, few
                Message 7 of 9 , Nov 4, 2008
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                  Power and ground are transposed on the byte interface? Might be good
                  to buffer Q there if possible.

                  Why not use a larger EPROM? 2716's are getting rare, few CMOS
                  versions, etc. The rom is decoded for 32k, what about a 27C256?
                  (Same argument for a 62256 ram.)

                  The '139 in the ram decode doesn't seem to be needed. Maybe not your
                  U7 pins 4,5&6 either. What if you ran U6 pin 12 straight to U7 pin
                  2? If you want a memory inhibit, keep the NAND at U7, tie R14 to it
                  and use U6-13.

                  R14 at 10K is too high for LS? Change to 100 ohms or use HC or HCT,
                  etc.

                  74LS154 may not work for CD4515, CD4515 has an internal latch.
                • ddmaow
                  Oops! Just realized using U7 for memory inhibit would t work. Please just disregard. Wish I could edit the post. My apologies.
                  Message 8 of 9 , Nov 5, 2008
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                    Oops! Just realized using U7 for memory inhibit would't work. Please
                    just disregard. Wish I could edit the post. My apologies.
                  • Doug Jackson
                    Thanks for that, this is exactly the sort of feedback I was looking for. Given the bursty nature of my work, I have not been able to touch this project for
                    Message 9 of 9 , Nov 6, 2008
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                      Thanks for that, this is exactly the sort of feedback I was looking for.

                      Given the bursty nature of my work, I have not been able to touch this
                      project for quite a while, but things are likely to slow down in a few
                      weeks. I will apply the changes you are suggesting.

                      Happy to replace the eprom and ram - yes, getting smaller parts is tricky.

                      Thanks again.,

                      Doug


                      ddmaow wrote:
                      >
                      > Power and ground are transposed on the byte interface? Might be good
                      > to buffer Q there if possible.
                      >
                      > Why not use a larger EPROM? 2716's are getting rare, few CMOS
                      > versions, etc. The rom is decoded for 32k, what about a 27C256?
                      > (Same argument for a 62256 ram.)
                      >
                      > The '139 in the ram decode doesn't seem to be needed. Maybe not your
                      > U7 pins 4,5&6 either. What if you ran U6 pin 12 straight to U7 pin
                      > 2? If you want a memory inhibit, keep the NAND at U7, tie R14 to it
                      > and use U6-13.
                      >
                      > R14 at 10K is too high for LS? Change to 100 ohms or use HC or HCT,
                      > etc.
                      >
                      > 74LS154 may not work for CD4515, CD4515 has an internal latch.
                      >
                      >
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