RAM problem (built 12 of 2007)

[TheatreSmith]

OK, I'm trying to upgrade a handful of iMacs that were built in 2007 which are running 3GB but say they can handle 4GB. I achieved the 4GB by dumbing down an equal number of 3GB machines.

None of the upgraded machines boot, but will once I replace the 1GB RAM back. What am I doing wrong, or not thinking about?

 

[rkaufmann87]

OK, I'm trying to upgrade a handful of iMacs that were built in 2007 which are running 3GB but say they can handle 4GB. I achieved the 4GB by dumbing down an equal number of 3GB machines.

None of the upgraded machines boot, but will once I replace the 1GB RAM back. What am I doing wrong, or not thinking about?

2007 iMacs (they should be 7.1 in About this Mac) can handle up to 6GB of RAM. You need to install 1x2GB and 1x4GB DIMM. OWC makes a kit and Crucial also can supply the RAM. This would be a wiser upgrade than 4GB as it gives 50% more RAM.

Also iMacs are VERY sensitive to quality RAM and it MUST be the correct specifications. Chances are the RAM you are trying is cheap or of inferior quality. Return it and buy Crucial or OWC.

 

[TheatreSmith]

I didn't actually buy the RAM... I salvaged it from another iMac (from the same shipment)

Full disclosure, I work for a school and have no budget to purchase RAM - hence the hack job on the spare.

 

[BrettApple]

Same speed? 667MHz? Same brand? Same latency even?

I've got 2x 2GB OWC RAM in my '07 and it's been flawless since 2012 when I put them in. I had 6GB in a similar '07 iMac too that ran fine as well.

Some Macs will boot with an 800MHz stick and one 667MHz stick since it will down clock, but if both sticks are running at 800MHz it will not boot.

My guess is the 2GB sticks might be 800MHz and the stock 1GB stick is still at 667MHz thus letting it boot up. But when both 2GB sticks are in it will not. Might be something to check. I know my Early 2008 MacBook was like that, very picky.