Well, I got real brave and opened her up and found the memory....WOW was I surprised-such tiny little memory. And of all the hundreds of memory sticks I have, I don't have the first one that will work. And the ones I've seen on eBay are not too expensive, but are they the ones I need? I'm looking for PC66 SO-DIMM modules, and they are running around $10 each, which ain't bad, but are they the right ones?

That will work in the top slot and bottom slot, the slot under the processor needs the low profile chip, it's a tight space. You can put in 512 M max, 2 x 256 M chips. The low profile can go in the top.

From the looks of the chip it's the low profile 1" model, since it's laptop too.

Here's the 2" chip. http://ramjet.com/ItemDescr.asp?Item=iMac128

Well, unfortunately, I only have ONE slot under the protective "cage", and one to it's left.

I bought some 128MB PC66 144 PIN LAPTOP SO DIMM memory, but when it got here, I found one stick in the machine was just a little different from the other. The difference between the two was so slight, I didn't notice until I tried to replace them both. The notch of the one not under the cover was about 1/16" farther over, so of the two I bought only one was useable. See diagram:

Both sticks I see inside the machine are 2 1/8" long, and I don't see anything else. The one I replaced is the 64Mb stick, so with the 128 I replaced it with, I now have 160Mb (vs 96)

I've looked all over the internet for the "other" stick of memory, but cannot find it listed anywhere.

Is anyone familiar with this difference, and can you steer me in the right direction?

Thanks

I don't know of a difference, maybe something is wrong with that stick?

According to EveryMac, you have the correct modules, and there are only 2 slots in that iMac.

That slot with the 1/16 off is the VRAM expansion slot, it can take a 4M chip.

Like I said in my other post, the second slot is under the processor. In other words it must be removed to get to the second slot.

VRAM

Another VRAM.

The iMac-350 we used to have had two slots - one upper (easy to get at) and one lower (immediately under the upper slot) that you had to remove the upper RAM module to get at IIRC.

I've been trying to take pictures of the chips, but my camera sux and does not take good pictures of small objects. But the 'notches' on the chips are offfset by 1/16". There is NO way that they can be exchanged with each other. So, I'm going to have to find the exact chip I need to replace the other one.

Sounds like the board was not stamped correctly (notch in the wrong location). Can you return it?

What is your website about?