[hudson1]

I'm thinking of buying a new 20" iMac in the not too distant future. The differences between the 2.0 GHz base model and next-up 2.4 GHz model mostly matter to me in the graphics card. I have an external DVD burner that works great and the HDD size is far more than I anticipating using anytime soon.

So the biggest difference that I would see is the Radeon 2400XT with 128 MB memory and the Radeon 2600 with 256 MB memory. Is anyone familiar enough with both cards to comment on how they compare to each other in real world use? Any links to performance comparisons between the two iMacs? Thanks.

[ghporter]

If I recall correctly, ATi's "XT" cards are less capable than their non-XT cards, so going for the step up model will get you both a more capable card AND twice the video RAM. Just upping the VRAM is a good thing by itself.

I'm running a 20" aluminum iMac with the 2.4GHz processor and the Radeon HD2600 with 256MB of VRAM. Also note that the upgrade model comes with a larger hard drive-a definite plus.

[mduell]

If you're looking for graphics performance, buy the previous generation iMac with the 7600. If you really want the look of the current generation, here's a comparison in a number of games; looks like R2600 gives you a 33-75% performance increase over R2400.

Originally Posted by ghporter 

Just upping the VRAM is a good thing by itself.

VRAM by itself is pretty much useless; look at the benchmarks for 8600M GT at 128MB, 256MB, and 512MB (at the same clockrate... Apple usually does some VRAM/core clockrate fiddling between generations). Some apps (Aperture comes to mind) can use it, but most games are unaffected by it (and may even run better because the cards with less VRAM often run it at higher speeds).

[EdipisReks]

Originally Posted by ghporter 

If I recall correctly, ATi's "XT" cards are less capable than their non-XT cards

my understanding is that XT cards are clocked higher than the non XT cards, but i might be mistaken, i haven't really paid that close of attention to video cards since i switched to the Mac platform in 2002.

[P]

For ATi, XT is the highest suffix - or second highest, if there is an XTX - followed by Pro and "neutral", or no suffix. They do not currently use a negative suffix, but when they did it was LE, SE or LT.

nVidia, on the other hand, has used the XT moniker as a negative suffix, but I don't think it ever was used for Macs and they don't use negative suffixes anymore.

[ghporter]

Ok, I got it backwards. But the 2400XT is still a lower-performing device than the 2600. Sorry for the confusion; my references were not available at the time (i.e. the network at school was going weird on me and I couldn't get anywhere but the school's domain, Yahoo, and MacNN).

[P]

Correct. If I may continue my explanation of pointless details in GPU naming, the number is always more important than the suffix. The intention is for all cards of the same number to have the same base GPU, and that the suffix tells if parts of it have been disabled and how highly clocked it is. There are exceptions, but they are very few.

ATi's latest generation does away with the suffixes completely, and uses just numbers. At least I prefer it that way.

[Simon]

Originally Posted by P 

ATi's latest generation does away with the suffixes completely, and uses just numbers. At least I prefer it that way.

I fully agree.

Anyway, here's a list of all previous ATI suffixes and what the logic behind them is.