iMac Extended Desktop Mode


macrumors regular
Original poster
Sep 4, 2006
Vancouver, BC
I am planning on purchasing a 17 or 20 inch iMac C2D (hopefully a 20 if I can convince my parents), and I was planning on using a 20" CRT Monitor that I already have for extended desktop. Does anyone know if this will hurt performance, or if I should upgrade to 256mb gpu memory, or 2 gb ram?


macrumors 68020
Nov 14, 2003
Washington, DC
generik said:
You can't upgrade the GPU.. that is a priviledge reserved for PCs and Mac Pros only :)
Not (as) true any more. Among the BTO options for the new iMacs, you can order the 20" with either the base 128MB VRAM ATI X1600 or for $75 extra a 256MB version of the card. And on the 24" iMac you can the base 128MB NVIDIA 7300GT or for $125 extra a 256MB NVIDIA 7600GT.

As to the OP's question. I dunno. From my experience, my 1GHz eMac (640MB RAM, 32MB VRAM) has some trouble displaying high-resolution video on my 20" second monitor while I do other things on the main 17" monitor, but that's probably processor power not VRAM as the problem.

My guess is, either card can handle two 20" monitors just fine.


macrumors 6502
Mar 31, 2005
London, England
Either card can handle both monitors, but I'd recommend the upgrade to 256MB if you can afford it. You'll notice some improvement in performance when you have lots of windows open, and when you use graphic-intensive applications. This effect will be more pronounced than it is for users without a second monitor, so the upgrade is definitely worth it.