Posted to the Colo(u)r Classic forum but cc'd here because it's relevant
and there are some folks here who are/were EEs and might have more ideas...
Just got finished talking with Velocity Upgrades about their 64MB RAM
chips. Rob, their head tech, claims they tested all variants of the 64MB
72-pin module that they make (single-banked, double-banked, 2K refresh, 4K
refresh, etc.) and none of them worked in their test LC575 machine. I
don't believe him, at least not completely.
However, we did agree that an issue here might be the RAM controller used
in the various LC575s. I have two LC575 boards, neither of which works
with a 4K refresh, double-banked chip. I don't have any other variants to
test myself, so I'm relying on you folks for help here.
The RAM controllers are located next to the PRAM battery, between it and
the VRAM slots.
Controller #1 from LC575 logic board part no. 820-0464-B:
9446 (made 46th week of 1994)
ADN141A3
343S1091-A N
(M)(C)1992 Apple
--------------------
Controller #2 from Performa 578 logic board part number 820-0464-A:
AT&T
343S1091-A B
1042BE
9404S 47487743
(M) (C) 1992 Apple
-------------------
ROM chips are located on the underside of the board.
ROM from Rev B board:
341S1062 LO
(C)1983-93 APPLE
LH5348NE
SHARP 9448 D
341S1063 HI
(C)1983-93 APPLE
LH5348NF
SHARP 9451 D
-------------------
ROM from Rev A board:
341S1062 LO
(C)1983-93 APPLE
LH534FD9
SHARP 9408 D
341S1063 HI
(C)1983-93 APPLE
LH534FDA
SHARP 9407 D
I have a feeling that either Rob didn't really have them check it out that
thoroughly or there's a somewhat rare memory controller that works with
64MB chips.
Anyone who has had a 64MB chip working in their Mystic should also share
the information for their boards, if possible, in the format I posted here.
(Please give all relevant information from the RAM module itself as well.)
I'm determined to get to the bottom of this.
MicroMac claims their BigSIMMs work just fine; why is it that MicroMac can
make one and Velocity can't? I think Velocity would love the extra
business, considering the prices MicroMac charges...
cl
____________________________________________
Chris Lawson
Mac Daniel and Tech Reflections columnist, Low End Mac
<http://lowendmac.net/macdan/>
<http://lowendmac.net/techref/>
____________________________________________
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