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Date Posted: 19:10:53 08/13/01 Mon
Author: Chris Lawson
Subject: 64MB SIMMs sorted - FINALLY!

Also posted to the Quadlist.

If you don't read anything else in this post, read this line:

The LC575 works just fine with single-banked, 64MB RAM modules. It does NOT work with double-banked, 64MB RAM modules.

Now for the full story...

Velocity Upgrades comes through again. I called them back after getting information from Mr. S. Watanabe (on the CC Forum) about his 64MB modules and talking with several other vendors (most of whom were completely and utterly clueless about anything more than 32MB 72-pin SIMMs in *any* Mac) and talked with Rob again. I explained the situation, told him that I thought single-banked modules were the trick, and through some discussion, we discovered he had been testing his modules in an LC475, not a 575.

Velocity apparently has no 575 in which to test RAM, so he immediately suggested sending an EDO and an FPM module out for me to test myself at no cost. Of course, I took him up on this more-than-generous offer, and having received the chips and tested them, here's what I can report:

The 64MB, single-banked EDO SIMMs work fine in the 575. There are two slightly different models. They are both 4k refresh.

EDO-A, as I'll call it, is a double-sided module with 8 chips.
EDO-B is a single-sided 8-chip module that's slightly taller than EDO-A.

The 64MB, single-banked FPM SIMMs work fine in the 575. Again, there are a couple slightly different modules, both 4K refresh:

FPM-A has 8 chips (four on each side).
FPM-B has 12 chips (six on each side).

FPM-C2 is double-banked and has eight chips on a single side. Same form factor and layout as EDO-B.

As noted before, FPM-C2 does NOT work in the 575. In addition, it is ever so slightly too tall to fit under the retaining screw in the Colo(u)r Classic chassis. All the double-sided modules work fine and are short enough to fit the CC chassis. The EDO-B module is also slightly too tall to fit in the CC chassis but unlike FPM-C2, it works as a 64MB chip.

Those of you who don't care about anything but the 575/Mystic can stop here.

Because I was curious, I stuck the chips in a few other 72-pin Macs I have sitting around...

The LC III does NOT work with 64MB RAM chips of any description. It gave the chimes of death on occasion but not every time, and the times it didn't give the CoD it refused to boot (chimed and then no video).

Because of the above, I suspect the LC 520 and 550 will not work with 64MB modules either. I also suspect the Performa variants of the LC III and 520/550 will similarly not work, and that the Colo(u)r Classic II will probably also fail to boot with SIMMs greater than 32MB installed.

My general conclusion: the RAM controller on the 030-based Macs with 72-pin SIMM slots appears to be insufficient to recognise a 64MB SIMM. If anyone can prove this wrong, I'd love to know, but I suspect it won't happen.

Interestingly enough, MicroMac claims their BigSIMMs (64MB and 128MB) will work in *any* Mac with a 72-pin slot. That is, any Mac that will *fit* those things. From what I've heard, they're huge (about double the height of a normal SIMM). If anyone has a BigSIMM, get a hold of me. I have some questions for you :)

If anyone wants information on the rest of the Macs I tested (since they aren't CCs or CC upgrades, I'm not reporting information here), just send me an e-mail and I'll send you a copy of what I posted to the Quadlist.

cl

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Replies:

Trophy RAM -- Mr Moof, 07:31:29 08/14/01 Tue
- Re: Trophy RAM -- Chris Lawson, 15:23:16 08/14/01 Tue