24" iMac - Bigger Screen wants more RAM?

netdog

macrumors 603
Original poster
Feb 6, 2006
5,758
37
London
I have been absolutely fine with 128MB on my 20" iMac Yonah, but does a bigger screen need more VRAM? Will I be sorry if I get the 24" with 128MB?
 

DeSnousa

macrumors 68000
Jan 20, 2005
1,616
0
Brisbane, Australia
neonblue2 said:
You mean VRAM not RAM. But no it shouldn't make a difference.
That's what he asked :p

It is fine, but it would be nice. It also really depends on what you use the computer for i.e. games, motion.app, etc
 

Scarlet Fever

macrumors 68040
Jul 22, 2005
3,265
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Bookshop!
more vram

It looks like new features of X and XP are taxing more and more on the GPU. It doesn't cost a lot to double your VRAM, so i would recommend the 256 just for future proofing purposes.
 

robbieduncan

Moderator emeritus
Jul 24, 2002
24,638
61
Harrogate
With a larger screen you are likely to have more windows open, and larges sized (in terms of pixels) windows open. Each window is double buffered in main RAM and single buffered in VRAM to use the Quartz Extreme compositor. If you ever end up with so many windows that you run out of VRAM the OS will have to page windows in and out of VRAM to composite them. This is bad.

A window takes width*height*4 bytes of buffer space to store so a 100x100 window requires around 40Kb of VRAM for it's buffer in the compositor. This ignores the shadows around windows so it's probably double that with shadows.

The 24" iMac has a resolution of 1920x1200 so a single full-screen window requires 9000Kb or 8.8Mb of buffer. If we double that for shadows then we see that a single full screen sized window requires somewhere around 15Mb of VRAM. So with 128Mb of VRAM you will only get around 7 or 8 full sized windows in there (as you need to reserve a couple of full screen sized chunks for frame buffer and so on and shadows probably don't cost you as much as I'm allowing for).

If Quartz 2D Extreme ever gets turned on (where all compositing within the window and drawing of everything on screen at a low level is done on the GPU not the CPU) then even more VRAM will be required.

My recomendation: get 256Mb. It can't hurt.
 

aswitcher

macrumors 603
Oct 8, 2003
5,338
14
Canberra OZ
256MB is a small % of the TCO now, and its unlikely Apple have made it upgradable. Leopard should switch on even more graphcis - and you may want to attach a second screen which again bumps the price up.
 

FFTT

macrumors 68030
Apr 17, 2004
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A Stoned Throw From Ground Zero
I'm pushing my Dell 24" with 64 MB VRAM, so 128MB would be fine
for anything short of intensive graphics and 3D.

If you can afford the 256MB upgrade without too much trouble, go for it, but make sure you have enough left over to equip your new machine with at least 2 GB RAM.
 

combatcolin

macrumors 68020
Oct 24, 2004
2,283
0
Northants, UK
FFTT said:
I'm pushing my Dell 24" with 64 MB VRAM, so 128MB would be fine
for anything short of intensive graphics and 3D.

If you can afford the 256MB upgrade without too much trouble, go for it, but make sure you have enough left over to equip your new machine with at least 2 GB RAM.
Did the same with my old 64MB 8500 on my PC.

And you can run 1920 *1200 with a 32MB card.