Re: Faulty RAM on Apple IIc motherboard

[dempson@actrix.gen.nz (David Empson)]

In article <25JUL199603103854@vax2.concordia.ca>, spec@vax2.concordia.ca
(Mitchell Spector) wrote:

>   An Apple IIc (ROM 0) I bought the other day seems to have defective
>DRAM chips on the motherboard. They're soldered-in of course, so I'd
>like to know _exactly_ which chips need to be replaced. Conducting the
>built-in self-test reports back the following:
>
>     *RAM ZP 0 0 0 0 0 0 1 0 0
>
>(I know the 1's are 'bad' chips, but which end would that be on and
>what is the "ZP"? Which of the sixteen 8K DRAMs are at fault here?)

ZP refers to "zero page", which is the first 256 bytes of RAM: the
self-test starts by testing this area thoroughly, so that it can be used
to test the rest of RAM (it can be used in several special addressing
modes).

This doesn't necessarily mean anything - the chip in question is probably
just completely dead, not just dead in a limited area.

Also note the '*' at the beginning.  I think this means that the test
failed in auxiliary memory zero page, not main memory.

The question then is which way to reaad the digits.  I'd say that if Apple
thought about it, they would show them on the screen in the same order as
the chips appear on the motherboard.

Thus you should work out which row is auxiliary memory, and replace the
sixth chip from the left (well - I assume it is the sixth chip: you have
one too many digits in that status report!)

-- 
David Empson
dempson@actrix.gen.nz
Snail Mail: P.O. Box 27-103, Wellington, New Zealand