Ram upgrade for Imac 27in i7

[Archaea]

Im about to order the Imac 27in i7 with the 4gb ram, if i buy 8gb
(4gb x 2)http://eshop.macsales.com/shop/memory/iMac/DDR3_21.5_27 and add with the 4g (2gb x 2) I will have 12gb of ram then? Are you able to do this? is there an advantage of buying 4gb x 2 over 2gb x 4 other than having 2 more ram slots?

[spinnerlys]

2 x 4GB = 8GB

2 x 2GB = 4GB

4GB + 8GB = 12GB not 16GB.

You have 4 RAM slots which you can use like you want.

2 slots are already taken by the 4GB (2 x 2GB), so for you the get 16GB you have to buy 4 x 4GB and get rid of the 2 x 2GB.

[TMRaven]

Only the ability to have 16gb of ram :)
I don't see any practical use in having over 8gb of ram though.

If your'e a big time enthusiast, you might try using PC10666 ram instead of PC8500 ram. The lynnfield will probably benefit from the extra memory bandwidth.

[Archaea]

Im going to be using it to render a lot of HD footage. So you think that its pointless to get 12 over 8?

[spinnerlys]

Im going to be using it to render a lot of HD footage. So you think that its pointless to get 12 over 8?

It's not pointless, but may be over the top, as rendering does not profit as much from the RAM as it does from the CPU, but the more you have, the merrier you are.

If you don't have a problem with spending money on RAM, then go for it.

[computergek80]

Only the ability to have 16gb of ram :)
I don't see any practical use in having over 8gb of ram though.

If your'e a big time enthusiast, you might try using PC10666 ram instead of PC8500 ram. The lynnfield will probably benefit from the extra memory bandwidth.

Wouldn't the extra speed in the PC3-10600 (DDR3-1333) be limited to the iMac's 1066MHz bus?

[Raima]

My i7 sits on 7.6gb of ram usage on a regular basis. I'd pop in more ram if it was more affordable, then I could run another VM instance.

[NiuFengLe]

Putting higher speed RAM will only result in wasted money. The RAM speed is gated by the bus speed and will only go as fast as the bus allows.

[TMRaven]

Although the lynnfields don't have a frontsidebus, they have a memory controller which can take ddr 1333hmz ram. This is so they could achieve decently high memory bandwidth in comparison to older generation i7 920s, which are triple channel memory, but can only take up to 1066mhz.

[seveej]

Putting higher speed RAM will only result in wasted money. The RAM speed is gated by the bus speed and will only go as fast as the bus allows.

Although this might be pure balderdash, Apple are known to often have HW features which are either just not advertised/documented or then disabled by SW.

IMNSHO, it would not make sense to have the same memory bus throughput in the C2D and i5/i7 -platforms. As the mobo is different anyhow I would not rule out that the i7 in fact would be able to run the RAM at higher speeds...

Can anyone verify this?

EDIT: Found it myself: http://timon-royer.com/en/52/is-it-possible-to-use-ddr3-1333-ram-with-the-27-imac-core-i5-and-core-i7/

Pekka

[TMRaven]

Yes, it's very possible to have 1333mhz in a lynnfield mac-- their memory controllers allow it. There is no dependency on a motherboard or northbridge and frontsidebus, because lynnfields do not use them. The lynnfield is a very integrated chip, and has an integrated memory controller rated at 1333mhz ddr3.

Geekbench scores are also not very good means of determining ram performance! First off, it's an artificial benchmark. Second off, I feel it's biased towards raw cpu performance, sadly.

You'll probably see better performance differences out of real life tests with photoshop scripts, gaming fps etc.