Have a 2007 21" imac. friend installed 2, 4GB memory for me, Apple genius says that's what causing slow downs on my machine? when they tested it only had a 4GB & a 2GB cards, so someone along the way did a switch on me. Apple says my machine can only handle 4GB total. i wonder if that's true? seems like it ran quite well for a long time, & it used to corroborate that it had 8 GB memory, so something fishy has occurred. machine is running quirky & would like to have max memory. Would appreciate some knowledgeable input…
IMac – Max memory for 21″ 2007 iMac
imac
Related Solutions
As seen in Apple Discussions your iMac has the SATA2 controller.
Also there are no limitations from the controller for the cache size of the HDD.
So you may easily go for an 7200 SATA2 16MB/32MB cache
note: The last 17" iMac, was the late 2006 model which I assume thats what you have :)
edit: Even if your iMac is SATA 1, it wont have any compatibility problems. It will just perform as much as it can (1.5Gbps/s)
last edit: If you use this tool you can see successful user upgrades and benchmarks of various hard drives.
If you have the 27" iMac MacTracker says it supports up to 32GB, even though Apple only says it supports 16GB. The 21.5" iMac can only support 8GB either way. OWC, a reputable memory retailer, started selling 32GB upgrade kits for the 2011 iMac last year.
Best Answer
Crucial, UK state that 4GB is the maximum amount of RAM that your iMac officially supports.
If you put more in and it worked then this could be seen as a 'bug', and wouldn't be supported by Apple. Such abilities could also be revoked through software/firm was updates.