8800B Turnkey Module
- I just spent some time studying the Turnkey Module, and gathering together the various documents related to this board. As far as I can tell, this board never had a stand-alone manual - its documentation was included in the 8800bt manual only.
There were two versions of this board. The earlier version had 1K of 2102 RAM chips directly above the four EPROM sockets; the newer version did not. The older version often had an extensive rework done to it (which actually does not work properly.)
I have documented what I learned about the various versions of this board in a file called 8800b Turnkey Module Notes, and published this, along with "complete" Turnkey board documentation in the Files section of this site, under "8800b Turnkey Module."
If you are using the Turnkey Module (either in an 8800bt or an Altair that has a front panel), then you will probably find this documentation useful.
- Great work! I always liked using the mod and never new it did not work. I'm Thinking from the viewpoint of an application programmer at PCC in Chatsworth, CA.1) It would have been nice to have hardware manuals, but they were in Albuquerque.2) Application programmers were not inclined to read (or understand) hardware manuals and too busy putting out fires to read anything but BASIC code.3) There were so many problems that we were not allowed to address problems unless there was a lawsuit pending.4) The board had a short lifespan because everyone was moving to the PCC 2000.Your notes mention the behavior of BASIC. Does the behavior you describe also apply to BASIC 4.1? BASIC 5.0?I'm wondering how many people used the board other than users of the Accounting Software. The mod was created because only the PCC Accounting Software required 64K.Some problems may not have been seen because it was considered bad practice to restart BASIC by jumping to location 0. TURMON users would only use .J17740. The standard behavior was to have Reset Jump to the boot PROM.At some point in development developers were required to OUT 255, FF before running the Application Software. I think that requirement changed over time. That makes me wonder if BASIC or the Accounting Software was changed to correct for hardware behavior..> (which actually does not work properly.)Thinking of Phillip Crosby's definition of Quality. If the requirements was to meet specification, then the board "worked" for the intended application (PCC Accounting software)..Thinking of Edsgar Dijkstra's definition of the USA view of "Correctness" - OK if it sells.The PCC definition was OK if we are not getting sued.Regards,W. Tom S.
- Yes, gotta love that Yahoo editor!I haven't confirmed the operation with the various Basic versions, but I bet they are all the same in this regard.There has been a misconception that an OUT to FFh would disable the PROMs. This is not true, once the Service Bulletin 007 rework was done (and the board actually matches the 200372-01 schematic) - PROMs are disabled only with an IN from port FEh or FFh. (MITS allowed FEh to disable the PROMs simply because the NAND gate that qualified the address was out of inputs :-) ) Prior to this rework, and with the reworked Rev 0 board, *any* IN our OUT instruction *might* disable the PROMs. The un-reworked circuitry allowed for either IN or OUT, and the I/O address were not qualified by relevant timing signal - so the Phantom flip-flop would see a glitch at the beginning or end of any IN or OUT cycle. I actually observed this on my own board. This bad behavior is what led me to dig into the Turnkey Module, and actually understand what was going on.I will soon release a new version of MBL and UBMON that will work with the Turnkey Module - at least one that is reworked correctly. My CDBL (combined boot loader PROM for 8" disks and Minidisks) will already work with a Turnkey Module, as will my HDBL (hard disk boot loader).Martin E
- I probably spread the misconception about OUT to the sense switches. I got the information from the System Programmers at the MITS factory. That may have been before the service bulletin. W. Tom S.
- If someone is interested to make a new TunKey PCB (PCC version w/o the RAM).I have high-res images (120MB) of an unpopulated PCB. Frank