Re: HP 1000 A400 repair #HP1000

Glen Slick

On Sun, Nov 29, 2020 at 9:35 PM Roland Dietiker <roland.dietiker@...> wrote:

Hi Rainer

I propose to exchange the VCP EPROMs (U908 U1108, 2764 EEPROMs) and check if the error allready persists. This is the easiest way to exclude an error on VCP EPROMs.

If this not change the situation, let me know which FW revision the board contains: partnumber of the firmware ROMs 12100-800xx (212, U312, U1412, U1512, U208).
The Communicator/1000 for Software Update 6.0, 5961-6201, December
1992 manual lists these 4 sets of part numbers for the A400 microcode
PROMs U1212 - U1512:

12100-80010 - 12100-80013
12100-80015 - 12100-80018
12100-80019 - 12100-80022
12100-80023 - 12100-80026

As far as I can tell there might actually only be one version of the
microcode for the A400. The different part numbers might just mean
different blank PROM parts, that is 4K x 8 vs 8K x 8, and different
part vendors.

I have one A400 CPU with DM87S421 4K x 8 PROMs screen printed with the
12100-80010 - 12100-80013 part numbers. I dumped the contents of
those PROMs and they are identical matches for the
12100-16005_Rev-4012.src - 12100-16008_Rev-4012.src ASCII-Hex file
format source for those PROMs in the HP 1000 Software Archive. And
those appear to match the A400 microcode source files
12100-18003_Rev-4012.src and 12100-18002_Rev-4012.src and the
assembled listing files 12100-17005_Rev-4012.src and

I have two A400 CPUs with CY7C263 8K x 8 PROMs (actually OTP EPROMs)
screen printed with the 12100-80023 - 12100-80026 part numbers. I
dumped the contents of those PROMs and they are identical matches for
the 4K x 8 set 12100-80010 - 12100-80013, but with the first 4K half
set to zero in the 8K set. The A400 CPU schematic shows that the CS3 /
A12 pin of the microcode PROM sockets is tied to a +5V pullup so only
the second 4K half of the 8K PROMs is accessed.

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