Curious quirk with iMac A1197 ram???
I've recently restored an iMac A1197 2007 1.83ghz Core 2 duo model. This is my first ever Apple computer and the transition from it being found unworking, next to a dumpster, to me having completely fixed it by upgrading and replacing the HD and installing snow leopard, have been extremely rewarding while also propelling a new-found curiosity about Apple software and hardware. This has led me to seek out any avenues to upgrade the hardware wherever possible.
Today I went to a consignment store with a computer section and dug through their entire stock of loose ram to find the only 2gb stick they had that was compatible with my iMac, which I found with a 256mb stick and a 1gb stick. When I placed the stick, naturally I wanted to replace the 256mb stick with the new 2gb, bringing my ram to the maximum 3gb but much to my chagrin, all 3 ram sticks will work in any combo but the desired one.
The ram it had originally are 256mb nanya and 1gb crucial. The new 2gb is nanya as well. If anyone has a guess as to why this is the case or maybe recommend a solution, it would be much appreciated. If not, I do plan to go back to the store and take my computer in to test the other 1gb sticks for compatibility. There are many 1gb sticks and they're all $1 each(even the 2gb was $1), so hopefully I'll find a different combination that gives me access to the full 3gb.
TLDR: 1GB stick and 2GB stick of ram not working together but work independently or when paired with a 256MB stick that I also have.
Try two 2GB sticks. You should still only have 3GB available but now the RAM will use interleaved access for an approximate 10’ish percent performance improvement.
Note: your 2 & 1 GB combo should have worked, so I would wonder if new stick was not playing nice electronically. Or the old was not playing nice