Intel iMac RAM upgrade question

[TheVoice]

Hi guys, asking this on behalf of a Mac-owning friend, hope you can help.

He's currently got an iMac 17" with 512MB of RAM, but wants to upgrade. He'd really like 2GB but after looking at RAM prices (£75 per 1GB DIMM), it seems that for 2GB, it's quite expensive, especially because he obviously can't use the 512MB he already has.

Would simply adding a 1GB DIMM (for a total of 1.5GB) still be fine? I know how reliant Intel architecture is (or at least, was) on Dual Channel; would he lose this by adding a 1GB alongside the 512MB, and what kind of performance hit would it be?

Thanks for any help.

[BlackDwarf]

Addming a gig should be fine. Pretty sure I could throw a 512 stick in my 20" and all would be ok.

[Spud1]

2gig of DDR2 is only 110quid @ scan...

http://www.scan.co.uk/Products/Produ...oductID=217961

As for only putting in one stick - not sure for iMacs but for macbooks (none-pro) it's a bad idea, as not running in dual channel mode causes big performance problems with the graphics card (due to shared mem).

I would still advise upgrading in pairs..

[Mike Fishcake]

The iMac uses a radeon x1600 with 128MB of video RAM, so it shouldn't affect that, however, as for dual channel performance, I have to say I don't know.

[TheVoice]

2gig of DDR2 is only 110quid @ scan...

http://www.scan.co.uk/Products/Produ...oductID=217961

As for only putting in one stick - not sure for iMacs but for macbooks (none-pro) it's a bad idea, as not running in dual channel mode causes big performance problems with the graphics card (due to shared mem).

I would still advise upgrading in pairs..

Found this:

http://www.scan.co.uk/Products/Produ...oductID=353418

It's 667MHz, which seems to match the specs on the Intel page. The one I had found before was this:
http://www.smcdirect.co.uk/detail.asp?id=161282

It says it's iMac specific, is there any actual difference?

Thanks a lot for the help.