[Techtoolslist] Ram Diagnosis Help Needed

[John Robertson]

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 :-#)#

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