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question though, if this is true, then y is the HD 2900 XT benchmarks not always better then the 8800 GTS 640mb or 320mb? The HD 2900 XT has 320 shader processors which is 2-3 times more then both 8800 GTS cards. From what i read, something with the "bandwidth" makes the 8800 GTS better then HD 2900 XT, probably because its higher then the HD 2900 XT. I dont understand it too well, mind if u explain this to me plz?
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The reason why HD2900XT doesn't perform as good as 8800GTS in some games is because of the low number of TMU. HD2900XT has 16 TMU, 8800GTS has 24, and GTX/Ultra has 32
There might be other reasons, but this is the only thing that I know.
EDIT: I also found a post from other forum that explains to you why the 320 stream processors in HD2600XT is not similar to the 128 stream processor in GTX
The post can be found here
8800 GTX vs. HD 2900 XT - SLI Zone Forums
And I will quote the post here
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You guys need to read the fine print. The 2900XT does not have 320 Stream procs like the 128 on the 8800GTX. The ATI more acurately has 64 packs of 5 stream procs. While each stream proc can handle up to five operations per clock, they can only work on one stream at a time. This equates to the GTX calc 128 parralel threads and the 2900 calc 64 parralel threads yet the 2900 can POTENTALLY calc 5 instructions per thread per clock while the 8800 only calc's one. Unfortunantly, while the 2900 can keep all 64 5 block shaders busy, it is difficult to keep all 5 blocks in a shader busy, meaning the 2900 isnt always running 5 operations on a thread. On a worst case senerio (not executing 5 instructions per thread) the GTX does twice the work per clock (128 vs 64), and on a best case senerio (executing 5 instructions per thread) the 2900 does 2.5x's the work than the GTX (128 vs 320). You must also realize the 8800 sharder clock is much higher (~1.5 vs ~.800). Performance will depend more on the way the game is programed with the 2900 XT. Point being, comparing stats is like comparing apples and oranges. These are very much diff types of cards.*
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