Mac Forum / General / Hardware / January 2006

I agree OWC is a good vendor. I have bought all my memory & hard drives
from them.  But I am sure other reputable RAM dealers are good too. Any
could likely answer your questions.

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I have a iMac G4 1.25GHz 17" USB 2.0 iLamp model like yours. I just
recently put a 512MB DDR DIMM in it from OWC adding to the original
256MB for a total of 768MB. It was easily added to the lower user
accessible RAM slot. It runs much better now currently under 10.4.2. I
could not afford the 1GB DIMM OWC lists for the iMac 1.25MHz which I
assume was also for the lower user accessible RAM slot. Utilizing the
1GB RAM would easily allow for 1.5GB total for these iMacs.

Historically, I recall some users opening their iMacs and replacing the
Apple supplied memory in the upper memory slot. It is not particularly
easy to get to the upper slot (involves proper torque of screws for heat
sink cooling & new thermal paste) but can be done (I have not opened
mine). I vaguely recall (don't quote me) that the RAM type for the upper
slot was different (# of pins?) than the lower. At that time in the
past, I think users who did the upper replacement were putting 512MB
upper and same lower for total of 1GB (probably the largest DIMM that
was available RAM at the time).

MacTracker 4.0 says for iMac 1.25GHz USB 2.0 (mine)
Max RAM: 2 GB
Type of RAM SLOTS
  1-PC2700 200 pin SO-DIMM (user accessible)
  1-PC2700 184 pin SDRAM (factory installed)

for yours (iMac 1.0 GHz)
Max RAM: 1536MB actual 1024MB (Apple)
Type of RAM SLOTS
  1-PC2100 200 pin SO-DIMM (user accessible)
  1-PC2100 184 pin SDRAM (factory installed)

which is somewhat as I recalled, the upper & lower slots being different
RAM types at least # pins.  So according to this, I could have 1GB
upper, 1GB lower for total of 2GB, & it looks as though yours is 1GB.
Looks a bit confusing on the description of yours tho, as it may go to
1.5GB total.

My iMac System Profiler lists:
DIMM0-J22 slot  -DDR SDRAM PC2700U-25330 512MB
DIMM1-J20 slot  -DDR SDRAM PC2700U-25330 256MB

for the user accessible slot with OWC 512MB RAM in it, and the upper
slot original Apple installed 256MB in it.

Hope this helps.

In any case, a reputable Mac RAM vendor should know & be able to advise
you before purchase (like OWC). Use one with lifetime replacement (like
OWC) as OSX seems to be quite particular about RAM.

Morenuf