MacIvory h/w debug notes

[chyde@chesapeake.ads.com (Clinton Hyde)]

back in the fall I began having really bad probs with my MacIvory. it
got flakier over time--sometimes it wouldn't boot, sometimes it would.
it did better if I shuffled board in their slots, booting almost every
time. eventually it wouldn't boot at all, giving me errors like "no
communications area" and eventually shutting itself down permanently.
so I got a replacement ivory board.

which didn't help. I got various repeats or the same messages. thought
maybe the disk was bad again, so i borrowed another drive, and was
able to get a working ivory partition built. so I thought I'd try the
old ivory board again (maybe the prob was fixed for it too?). Error.
neither ivory board would work again after that.

visited someone else and tried swapping hardware with their stuff.
that only served to show that my new ivory board was ok. just as we
were quitting, I got a new message saying something (I forget what)
about Parameter RAM.

hah! enlightenment occurs! I then got out the old XPRAM init which I
had archived somewhere. it completely zaps Parameter RAM on the Mac
motherboard. ta da! everything is back to normal. this also explains
the bit about why swapping boards would work: it appears that genera/-
ivory stores some info about hardware config in the PRAM, and the
board-swap would cause it to overwrite some of that, rendering things
OK to boot.

i still haven't tried the old ivory cpu (not quite that brave right
now).

but, the info learned is clear: if the ivory starts acting flaky about
booting, do the zap-pram bit right away. of course, if the darn mac
Genera app had told me this at the beginning, I wouldn't have had to
struggle so hard with it. so i'm here to tell you: zap the pram.

actually, that's probably a good idea anyway. do it today!

 -- clint