Re: Ram Diagnosis Help Needed

John Robertson wrote:
> Mark Hooks wrote:
>> I'm trying to learn more about how to interpret RAM read/write test
>> results
>> on Atari 6502 based games. Can someone recommend a good text book
>> where I
>> can learn more about how to sort out high from low bits ? The Atari
>> Cat Box
>> manual assumes you have this basic knowledge.... which I don't. I've
>> searched the archives and the FTP site to no avail.
>>
>>
>>
>> Mark Hooks
>>
>>
>>
>
> High RAM is data bits 4 - 7, Low RAM is data bits 0 - 3.
>
> Try this with the CAT box when it says there is a RAM error - write a
> memory location with "AA" then read it. Should be "AA" of course. then
> try writing "55" and reading that back.
>
> OK, so, lets say AA worked fine(10101010) but 55 (01010101)gave back
> 45 (01000101). This would mean that the Low RAM has a stuck bit (Low
> at that memory location) on data line 3. This is a VERY basic RAM
> test, but gives you the idea of how RAM tests.
>
> There are many web pages on RAM testing and the algorithms used,
> fascinating reading!
>
> John :-#)#
>
Ah, right, can't count...the error is on data bit 4, not 3...you count
from the right to left from least to most significant digit.

John :-#(#

-- 
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