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Memory fault

Posted: Thu Nov 16, 2017 10:02 am
by Oggyuk
Hi All
Does anybody know which IC has failed from the memory location 30804?
Thanks

Re: Memory fault

Posted: Thu Nov 16, 2017 12:51 pm
by martyn_hill
Hi OggyUK

That address is in the first 48KB of the memory-map, which on the QL is always ROM. Seems odd that you even got to detect this... Perhaps you mis-quoted the address or dropped a digit?

All DRAM is instead from 131072 (128k) upwards and, on an unexpanded QL, will be 'mirrored' every 256K.

If we are indeed taking about an address in DRAM, then because of the use of 1-bit DRAM ICs, the question becomes "which bits failed the memory test" - the actual address (that Minerva displays) only tells us which of the two distinct 64KB banks (ICs 1-8 or 9-16) are involved.

So, what were the actual word patterns written and what was read-back (I'm assuming you are using Minerva to tell you this, in which case the first line is what was written, the second what was read back, the third the first address that failed.)

Good luck!