Re: IIGS memory error

[Stephen Shaw <xstephenx@apple2.org.za>]

On 27 Mar 2002 22:29:11 GMT, ground.ecn AppleII Librarian wrote:

> In article <1f9g4mg.cqqicu12qqdw8N%dempson@actrix.gen.nz>,
> David Empson <dempson@actrix.gen.nz> wrote:
>>ground.ecn AppleII Librarian <apple2pd@garp3.icaen.uiowa.edu> wrote:
>>
>>> When I run the Claris memory test (MemoryCL) from AWGS on a Rom3 with 1Meg
>>> Apple memory expansion board, I get a memory error at $180582 .
>>
>>Is the same location reported each time you run the test?  I'll assume
>>that it is.
>>
>>$180582 is $100000 + $80000 + $0582.
>>
>>The motherboard has the first 1 MB ($100000), so the error is on the
>>memory expansion card.  The card has rows which hold 256 KB ($40000)
>>each, so the fault is in the "third row" on the card.
>>
>
> Thanks to David for his help and suggestions.  I took a slightly different
> approach to isolate two bad chips.  I haven't determined memory mapping
> for the 1Mb Apple expansion card yet.  Board with 256K shows memory to
> $12000 ???, with 512K memory goes to $16000 ???.  So I think MB = $80000,
> plus $40000 per 256K.  (I am trusting my memory here so I may be wrong.
> In fact, this can't be right).
>
> Using the system monitor (from basic call -151), I
> could see that at 18/0582 I had a chip with hi-bit stuck on '0' (80=00,
> FF=7F) and the same at 18/05a2.  But a memory move from one 256 byte page
> to another gave me really screwy values (lots of 7D ).
>
> Anyway, I did all my testing with 512K memory.  First I removed all 24
> chips, then used groups of 8 until I had a group of 8 that worked.  Then I
> swapped in four chips at a time to find a good groups of 4.  Then 2 at a
> time from the bad groups of 4 to get good groups of 2.  Finally I had two
> groups of bad 2 chips.  Then I found the two bad and two good chips.
> I used the memoryCL pgm from Claris AWGS for memory tests.
>
> So now I have 22 good chips :-)  and 2 bad :-(  I can't find a local
> source of DRAM but when I get some good 4256 chips, I will provide
> a memory test with 1 bad memory chips at each of the 24 locations
> (UA9-UA16, UB1-UB16)  (UA is top row, UB is bottom row).  This should help
> others figure out where a bad mem chip is located.  I just need to locate
> at least one good chip to start, but obviously I want two good chips.
> Thanks goodness it wasn't one of the 8 soldered chips.
>
>   --Steve

Why not trawl the thrift shops for memory chips from old PCs? The most common 
were 4164, 4464 and 411000. Most PCs used the 64 range. The number may be 
'buried' in the chip marking i.e. KM734464 etc.


-- 
... She said it was either her or the Apple II computer. I'm still posting