iMac G3 RAM vs. Powermac G3/G4 RAM

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iMac G3 RAM vs. Powermac G3/G4 RAM

I have an iMac G3 from way back when. It's got a 350 Mhz processor and it's green and I haven't had a chance to look inside it yet, but based on its age and specs, I believe it uses 168-pin RAM; older models didn't. Can I upgrade it with the same 168-pin RAM used in G3/G4 towers from the same era? I have a G3 Yosemite that chimed once but won't boot and has 4 sticks of RAM awaiting transplant to a more functional machine. I also have a Sawtooth that can lend a stick or two to the cause of making the green machine OSX-ready.

If it's compatible, does it matter whether I use PC100 or PC133? The towers don't care if I interchange them.

Posted on Apr 21, 2011 11:49 AM

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Answer 1

Niel

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Apr 21, 2011 4:54 PM in response to Maronan

Only if that RAM is capable of operating at PC100. A module which isn't will be ignored.

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Answer 2

Maronan Author

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Apr 22, 2011 3:38 PM in response to Niel

In the towers, the faster RAM runs slower in a slower tower. But is it even compatible between towers and iMacs?

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Answer 3

Niel

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Apr 22, 2011 3:39 PM in response to Maronan

See above.

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Answer 4

Jeff

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Apr 22, 2011 6:22 PM in response to Maronan

The iMac G3 and the Mini-Tower G3s and pre-MDD G4s use the same 168-pin, PC-100 or PC-133 SDRAM. Compatible memory can also be taken from PCs, as long as it isn't ECC, Registered, or parity. The memory from the B&W G3 can be used, although the largest supported DIMM in that model is 256 MBs, while the iMac can support up to a 512 MB DIMM in each of the (2) memory slots, for a total of 1 GB. Before attempting to install OS 10.2.x or newer on the iMac, you need to run the iMac 4.1.9 Firmware Update, if it hasn't been done already. The firmware update must be performed while the iMac is booted from the internal hard drive running OS 9.1, 9.2.1, or 9.2.2.

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Answer 5

Maronan Author

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Apr 25, 2011 8:07 AM in response to Jeff

OK. I pulled a pair of 128MB sticks from the G3 tower. One was listed as "not compatible" for some reason, so I switched it for a third stick. Now the iMac has 256 MB RAM and runs OSX 10.2 (and will run 10.3 as soon as I figure out how to turn my G5 tower into a Netboot server for the install).

Thanks.

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Answer 6

Jeff

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Apr 25, 2011 11:27 AM in response to Maronan

Other than being defective, the only problem I could see with a 128 MB DIMM that's supported in a B&W G3 but unsupported in a G3 iMac would be related to the chip density. Does that 128 MB DIMM have 16 chips on the card (8 on each side)? Does the supported 128 MB DIMM only have 8 chips on the card, with all 8 on one side or 4 on each side?

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Answer 7

Maronan Author

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Apr 25, 2011 2:30 PM in response to Jeff

I can't say that it was "supported" in the G3 B&W, just that it was in it. The B&W is defective (won't boot, won't even load open firmware, has chimed a few times but now won't even do that) so I can't comment on whether it liked that particular DIMM; all I could verify is that it was physically installed. The iMac is the only machine that booted with the thing in it.

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Answer 8

Allan Jones

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Apr 26, 2011 10:25 AM in response to Jeff

Hi Jeff,

"Other than being defective, the only problem I could see with a 128 MB DIMM that's supported in a B&W G3 but unsupported in a G3 iMac would be related to the chip density"

I'm not so sure. I pulled a 256 from my Beige G3 and it wouldn't work in our G3/400 iMac even though the density was the same. I looked up the specs for the chip on OWC, from whom I'd bought that stick. The numbers didn't reveal anything useful but I noticed a statement that said "For G3 Towers only."

Never figured that out, but the resluts were pretty clear.

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Answer 9

Jeff

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Apr 27, 2011 12:44 AM in response to Allan Jones

"I pulled a 256 from my Beige G3 and it wouldn't work in our G3/400 iMac even though the density was the same... I noticed a statement that said "For G3 Towers only."

If you purchased it for a beige G3, the chip density could have been the same, but the memory could have been PC-66 (-10ns), which wouldn't be compatible with the iMac G3's PC-100 (-08ns) requirement. Also, the "G3 Towers only" restriction may have to do with the DIMM's height. The desktop models were limited to DIMMs that were 1.15" or less in height, whereas the towers didn't have clearance issues.

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