ATI/Nvidia, it truly depends on tastes, one could quote 100 reasons why nVidia's better than ATI, while another could reply with 100 reasons why he thinks the opposite, I doubt there is a true superiority of one brand over another; but if we're talking personal preferences, I for instance find ATI cards slightly technically superior to nVidia, but the reason why I opted for nVidia it is because they offer better drivers support and they are generally better supported by videogames. I am sure though, somewhere on the internet there's someone which prefers ATI for my exact same reasons, maybe reversed.
Pertaining your specific question this post may help:
The Nvidia GTX 260 core 216 55nm (the only card in the history of GPUs whos name is longer than its part number) contains:
216 cores @576 mhz
GDDR3 on a 448 bit bus with a mem clock of ~2000
and is on PCIe 2.0
The ATI Radeon 4870 contains:
800 cores @ 750 mhz
GDDR5 on a 256 bit bus with a clock of 900
and is also on PCIe 2.0
How do these cards perform on par?
ATI cores are divided by 5, dont remember specific reason. so basically its 216 cores vs 160 cores from ati.
Memory doesn't affect the speed of the graphics card, but rather the resolution u wanna play it on.
for example u can compare the speed of ati and nvidia memory by doing the following. The bit, in other words the bandwidth of information which can pass through is 512 bit having a speed of 1800mhz is the same as a 256 bit with a speed of 3600 mhz. Therefore bit multiplied by speed is the real memory speed.
Dunno what rop si maybe another guy explain that.
so the real comparison would be 216 core at 576mhz vs 160 core at 750 mhz.
448bit*2000 mhz vs 256bit*3600 mhz which is about the same.
In the end the cards perform about the same.
or if you want an insanely complicated explanation I found surfing around:
Edited by Mafia2020 - 4/21/11 at 7:14am