Re: Troubleshooting X/Lisa RAM boards - first draft

• On Fri, 3/25/11, James MacPhail <gg__at_email.domain.hidden> wrote:

> The Lisa's power-on self-test attempts to provide
> information for repairing memory boards.

<useful info snipped>

That's very interesting - and useful. I just tried all three of my faulty memory boards, and have some unusual results. Two of the boards are especially clobbered, and if you use them in slot 2, the Lisa won't even run the self test - it just gives two beeps and a scrambled screen. If moved to slot 1, however, they do allow the Lisa to run it's tests - which fail at an error 70. Here's the results of those boards:

Board 1:
00000186 0000 0000 0000 0000 1000 0800 0060 0100

Board 2:
00000186 0000 0000 0000 0000 00FF 00FF 00FF 00FF

It's obvious that board one has more than a few bad chips, and board 2 seems to have something wrong that affects the entire lower byte.

I tried the third board - this one will simply give an error 70 regardless of which slot it's in. I stuck it in slot 1 for consistency:

Board 3:
00000186 0000 0000 0000 0000 0000 0000 0000 2000

Since this one seemed the least broken, I decided to try running LisaTest. I was able to continue after the error and boot from floppy, but as the program loaded, the screen got corrupted with dots and retrace lines. LisaTest ran though, until it got to the memory test, where it crashed and reset the computer after about a minute.

I moved the board to slot 2, and tried again. Obviously, the data in location $186 is different, it now reads: 00000186 2000 0000 0000 0000 0000 0000 0000 0000

showing that the affected bank is now in a different spot in the memory map. Booting LisaTest is now more successful. No retrace lines or graphic glitches. It runs right through the memory test, and then the I/O board test - then the computer simply resets. No test summary like normal. So, yeah. LisaTest is pretty useless when it comes to testing Lisas.

-Ian

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