On 2000-10-16 [EMAIL PROTECTED] said:
>It is clear what is damaged in your computer.
>Your 8253 timer contains 3 16-bit timers counters and is attached
>to system bus. Output from timer 0 is attached to interrupt level 0
>and is used to generate an interrupt each 54.925 ms. Thanks to this
>timer system's time of day clock works and I/O routine too.
>Output from channel 1 is used to generate DMA request on DMA
>channel 0, this is used to refresh DRAM.
Thank you for your precise description of these timer chips; I should
have no problem finding them -- perhaps I will find the time to open it
up tomorrow!
>Since your timer is not working properly you got also parity error
>due missing refresh cycles.
If the PC/XT has a parity error, it does not report this. The parity
error was reported by my other AT machine.
>You computer starts but after it got hot it hangs, this MAY be a bad
>elettrical contact: remove and re-insert you 8253 chip. At least
>you must replace it.
There were some chips that seemed warmer than others, last time I opened
it. But I'll especially locate the 8253 chip you've mentioned and re-
insert it. It will be interesting to isolate and correct this error
once and for all! I had suspected that my problem could be caused by
overheating, but I assumed that this was only caused by a poor fan, not
a bad electrical connection due to an improperly seated chip. The
problem with detecting such errors was probably not included with this
otherwise excellent microcomputer service manual in my possession,
because these computers were still relatively new in the late eighties
(when it was first written), and "old age" problems were much rarer,
and so not covered in the manual.
By the way, the addition of the "STACKS=12,128" command in the config.sys
file may have corrected a software problem, but the lock up error
didn't change. :(
If I still have problems, I'll report back to the list.
So far, my IBM AT is working fine again, but I'll keep my eye on it, just
in case I notice a possible hardware problem with it.
Thank you *very* much!
Jerry [o:--] "The" IBM AT/5170 model 319 [--^~---] 9600kbps/30M HD
*1986 ||||||||||||||||||||||||||||||||||||| [ =====_] 512k RAM - 8MHz
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