iMac RAM upgrade madness

Are you sure this is a 2007 model iMac and not a late 2006 model purchased later?

What is your iMac model number identifier?

From what you describe, you may have a late 2006 model.

Those iMacs could take 4 Gbs of RAM, but only address 3 GBs of the total.

Apple allowed these iMacs to have have 4 GBs of RAM because the hardware/software architecture can take advantage of matched pairs of RAM.

All your ram meets the specifications show here iMac (Mid 2007): Memory Specifications

Actually, Frank maybe correct.

I just noticed you are running OS X 10.8 Mountain Lion.

You could only have this installed on a mid2007 iMac or later

So, your issue could be improperly spec'd out RAM.

Purchase reliable Mac RAM from either Crucial or OWC ( macsales).

Apple know-it-all wrote:

They're both PNY. It was 6400, rather than 5300, which I thought would still work. All of the other required specs meet up. Does it not work in this case?

Nope you have the buy the RAM specified for your machine, they will not run RAM designed for machines that were designed after it. I'd recommend contacting a reputable reseller of RAM such as OWC (www.macsales.com) or Crucial.

The speed of the chips is different from what I can see searching on the web. If your Mac calls for one then using the other could be cause problems.

The 6400's run at 800MHz while the 5300's run at 667MHz and it looks like your machine calls for the 5300.

In your case given the oddity of the symptoms I would think using the wrong chips could be causing the problem. The only way to know for sure is to get the correct chips and see what happens.

regards

I knew you would ask this 😉

The best I can tell you is that when dealing with timing issues anything and everything is possible. There is no way to say just what will work or fail. It is very possible that if you put those chips in a different 2007 iMac you'll get totally different symptoms.

All that can be said is if you are using the wrong chips and the machine is not working then putting in the right chips is the first step.

regards

I'm in the same boat only I did use PC2-5300. I have a mid 2007 imac and was also looking to upgrade to 4GBs and can only get 3 to run. Also, it only boots up if the GB stick is in the Bank0/DIMM0 slot.

I tried with two 2 GB sticks of PNY DDR2 PC2-5300.

The sales person said I could return them if it didn't work but that will have to wait until monday. I'll repost if I find a brand that works...

Lot's of problems in these topics with PNY RAM.

One good stick of RAM may allow the Mac to set the other stick to a useful setting.

BTW, you can put 6 GB from OWC in it...

At the Apple Icon at top left>About this Mac, then click on More Info, then click on Hardware> and report this upto but not including the Serial#...

Hardware Overview:

Model Name: iMac

Model Identifier: iMac7,1

Processor Name: Intel Core 2 Duo

Processor Speed: 2.4 GHz

Number Of Processors: 1

Total Number Of Cores: 2

L2 Cache: 4 MB

Memory: 6 GB

Bus Speed: 800 MHz

Boot ROM Version: IM71.007A.B03

SMC Version (system): 1.21f4

Systems been running slow. Running 10.8.3. I want to upgrade iMac memory and looked at OWC. I saw the 6GB. Can the older iMac take advantage of 6GB? I don't touch hardware often but it looks fairly simple. Here's my system info:

Model Name: iMac

Model Identifier: iMac7,1

Processor Name: Intel Core 2 Duo

Processor Speed: 2.8 GHz

Number of Processors: 1

Total Number of Cores: 2

L2 Cache: 4 MB

Memory: 2 GB

Bus Speed: 800 MHz

Boot ROM Version: IM71.007A.B03

SMC Version (system): 1.21f4

Any advice is appreciated!

Your computer needs RAM as shown below.

Maximum Memory 6.0 GB (Actual) 4.0 GB (Apple)

Memory Slots 2 - 200-pin PC2-5300 (667MHz) DDR2 SO-DIMM

You ought to be able to run 6GB. It is not difficult to fit and OWC will advise you.

Got it...thank!

You're welcome.