Sat 6 Sep 2008
This rec.puzzles newsgroup post made me laugh. I don’t read rec.puzzles or newsgroups in general, but this is completely out of place in rec.puzzles. He has stuffed so many technical terms into two paragraphs it’s just laughable. I really don’t know how much truth to what he is saying because I have never heard of a 555 timer, pulse width, write strobe, NAND timer etc. etc. etc…
The early Apple ][ was notorious for that. I evenutally unsoldered
all the sockets and replaced them with high reliability versions.The one time I had a guine memory failure wasn’t a RAM chip, though.
It was a NAND gate that passed the write strobe to the RAM chips,
so it could read memory but not write it. Obviously, the boot ROM
didn’t get very far. I tracked it down by attaching a 555 timer to
the reset line and slowly increased the pulse width until the address
lines went from stable to unstable. When I checked what opcode was
executing at that momement, it was the first return from subroutine
in the boot code. The gate must have failed due to vibration (output
was floating) because I had just transported the machine in my car
prior to the failure.
