Often I see/hear people saying "I have a 256MB graphics card, I should be able to run Crysis."
The fact that you may have 256MB of video ram on your graphics card is largely irrelevant. You may have 1GB of memory on your computer, but if it merely has a pentium-3 1.0 ghz, it still isn't going to run it at all. The video memory is a very poor indicator of performance, especially because graphics card companies like to pad the memory on lower end cards. They do that because low-end memory is cheap and makes it look faster than it really is.
In order to show how much 256MB cards can differ, I decided to collect benchmarks around the web. They will all have a fairly high end Core 2 Duo or so, an nvidia graphics card and they will demonstrate 3DMark06. This won't be an exact science, but it'll be good enough.
Here's hardwarezone's review of the 8800GT 256MB. I have this card in my desktop. They are using an Intel Core 2 Duo E6700 (2.66GHz.)
Resolutions: Score (with an 8800GT 256MB) : Score with an 8800GT 512MB
1280x1024: 10752 : 10968
1600x1200: 9541 : 9783
Next we have hardwaresecret's review of the Geforce 8500GT, but also showing off a few other cards. They used a Core 2 Extreme X6800 (dual-core, 2.93 GHz.)
Score with an 8600GT 256MB:
Score with an 8500GT:
Score with a 7300GT:
So the 8800GT is 634 % faster than the 7300GT.
Finally, we have the 7300GS 256MB. This reviewer used a slower athlon 64 x2 3800+, but that can't make too much of a difference.
(Unspecified Resolution, probably 1024x768 or 1280x1024):
But now, how about the ultimate question! Can your 256MB card run crysis at high detail? This was done using a an exact scientific comparison by Tom's Hardware.
ATI Radeon 3850 256MB: 25.50 FPS
ATI Radeon x1300 256MB: 1.90 FPS
The 3850 is 1242% faster than the x1300!
So simply put, a fast GPU with 256MB can barely run crysis at high detail, a slow GPU with 256MB can't make it playable at all.
So please, don't ever say "I have a xxxMB Graphics card."