[FireWire]

Hi! I've reached a point where 3 GB or RAM isn't enough anymore but I don't want to replace a perfectly good computer just for that. I've been wanting to upgrade the RAM for many years but all sources indicate that the system supports 4 GB but will only use 3 GB because of a chipset limitation.

However, I stumbled today on a Apple Discussion page that states that we can now install 6 GB? As a matter of facts, OWC sells an 6 GB upgrade kit (4+2). Will it really work? I'm highly skeptical... What do you think?

Also, in the event it really works, can I use any compatible stick or did OWC employ some special magic? (They only list their own RAM as being available in 6 GB configuration).

I have a mid-2007 20" aluminium iMac (7,1), 2,4 Core2Duo.

[Dex13]

this is the cheapest one I could find.

Newegg.com - Mushkin Enhanced Essentials 4GB 200-Pin DDR2 SO-DIMM DDR2 667 (PC2 5300) Laptop Memory Model 991685

Crucial is $1 less after the promo
http://www.newegg.com/Product/Produc...82E16820148220

These both are 200-pin PC2-5300 (667MHz) DDR2 SO-DIMM, which that imac accepts.

[Waragainstsleep]

Aluminium iMacs will take 6GB according to Mactracker.

[FireWire]

Great! thank you! Had I known before.. Why doesn't Apple update their spec to reflect that 6 GB is indeed supported?

Also, I noticed the 800 Mhz stick is cheaper, it will still work right? Also, as the bus is 800 Mhz, should I upgrade the other stick to the higher speed? And would it be best to put 2x4 to benefit from memory interleaving (with just 6 GB recognized) or it's not worth it?

[Edit] Mactracker says "Maximum RAM 6.0 GB (Actual) 4.0 GB (Apple)". In the documentation, Apple said it supported 4GB but only 3 will be usable. Will it be able to address the whole 6 GB or it only means that we can physically put 6 GB?

[Waragainstsleep]

Physically it will fit 8GB but it may not boot then. AFAIK the white iMacs are the ones that will only address 3GB. Yours should address all 6GB.

You need 667MHz chips, I have a feeling the 800MHz won't work in those for some reason. They may even be slightly different pinouts.

[FireWire]

OK, I'll play safe and only install 6 GB then. It's strange that 800 wouldn't work, as normally you can install faster memory but it will just revert to the bus speed. I'll pay the 5$ difference and be safe if you think it could not work! Thank you!

Side question: my Mac supports the 64-bits achitecture but it currently boots in 32-bits mode. Will it be able to address all 6 GB or will it be limited to 4? Is it safe to force the system to boot in 64-bits mode then?

[Waragainstsleep]

I think it has 64-bit memory addressing anyway but you should be able to persuade it to boot with a 64-bit kernel.

I have a feeling the 800MHz RAM won't physically fit. They are very similar but not quite right IIRC.

[SierraDragon]

Originally Posted by FireWire 

Side question: my Mac supports the 64-bits achitecture but it currently boots in 32-bits mode. Will it be able to address all 6 GB or will it be limited to 4? Is it safe to force the system to boot in 64-bits mode then?

It does not matter. OS X utilizes much more than 4 GB RAM. Better with only 6 GB RAM will be to stay in 32-bit mode because 64-bit takes more RAM overhead and 6 GB is not very much RAM. Unless War is correct and the 64-bit address space is taken even under 32-bit operation, in which case again it might not matter. In any event IMO generally best on older hardware is to stay in 32-bit mode.

Do note that many folks have alleviated difficulties with RAM under 10.7.1 Lion by reverting to 32-bit operation.

You do not state what OS version, but with that box I would stay with 10.6.8 until I was really really sure 10.7.x was not going to cause issues.

OWC at http://eshop.macsales.com/ will definitively answer the question about what RAM the box can utilize.

HTH

-Allen

[Waragainstsleep]

Switching Kernels:
Mac OS X v10.6: Starting up with the 32-bit or 64-bit kernel

Memory
Physical Address Extension - Wikipedia, the free encyclopedia

[FireWire]

Thank you everyone, I learned a lot today! I'm still running 10.6.8 so I'll stick with that for now.

Looks like you're right, 6400 memory could cause problem: https://discussions.apple.com/thread...art=0&tstart=0. The pinout is the same but strangely, it looks like one stick will work but not two... I'll pay the higher price and stick with 5300.

Also, as stated, I should be fine running in 32-bit mode : https://discussions.apple.com/thread...art=0&tstart=0. It will address my RAM correctly.

Thanks again! I'll be able to keep my trusty machine a few more years!

[FireWire]

I finally did it! I ordered a 4 GB Crucial stick and everything works fine! The machine is snappier and after one week my pageout/swap is still at 0 (it used to be huge!).