bad_haze

LOL, conspiracies everywhere!

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QuickSkillz

Considering how getting .7 more fps in the cpu bench along with tighter timings can get you over 4,000 more points when in reality you would only gain 5 fps in the game.

003

All other things being equal....

Now this is not to say that a heavily overclocked 3870 won't outperform the 2900. In fact, it is likely with the fixed bios that it will, but the 2900 will still pull ahead at high resolutions and possibly with more AA (depending on core clock) due to the significantly higher memory bandwidth.

If ATI had given the 3870 the same memory setup as the 2900, there would be no comparison.

rx7speed

are you SURE though that memory bandwidth is a limiting factor

QuickSkillz

It isnt, its like saying my cpu isnt able to do much work due to my RAM not being fast enough when in fact faster RAM might make like a 1-3 difference in fps performance and no difference in overall system performance besides benchmarks. The core/architecture is what makes the difference which is why you wont see much of a difference in fps when just overclocking the memory.

003

Memory bandwidth becomes limiting at high resolutions and with a lot of AA/AF.

Core speed has a more immediate speed boost at lower resolutions.

Yes, QuickSkillz, architecture is what makes the biggest difference. But the RV670 is not using any kind of radically new architecture. It is merely a die shrink with the addition of UVD+ support and certified for DX10.1 (and most if not all of the DX10.1 features happen to be supported on the R600 as well), plus a significantly weaker memory bus and a 256-bit bi directional ring bus (512-bit ring bus for short) as opposed to a 512-bit bi directional ring bus (1024-bit ring bus for short).

And there is no getting around this information, regardless of how you look at it. At stock speeds, the 3870 has slightly more shading power than the 2900XT. But that is because of the core clock ONLY. Once the core clock on a 2900 matches or exceeds that of the 3870 -- it will simply be faster, period.

This is NOT to say the 2900 is the better card. If I had the choice between a 2900 and a 3870 right now I would probably take the 3870, due to less than half the power usage and the support for UVD+, as well as higher potential overclocks. Although even with the fixed bios they don't seem to be overclocking much past 860MHz anyway.

pablo NZ

Hey 003, this may be an annoying question, but will the 256bit external memory bus on the 3870 be much of a limiting factor at 1680x1050 with 0xAA and 8xAF? You keep saying that it will bottleneck at higher resolutions with lots of AA/AF but I''m not sure how "high" you mean

003

Don't really know what the exact scenario would be, but let me put this in more simple terms.

A 3870 clocked at 500/1000 would be slower than a 2900pro/xt clocked at 500/1000. Again this does not really make the 2900 a better buy, considering what the 3870 offers.

Blue_Fire

2900 is aa bugged, at 1600x1050(or 1200) the 2900 will win with AA off, or low (4x) AA. but not any higher. In answer to your question pablo, no the 3870 would take lead in that scenario with anything higher than 4x. The only reason that 512 bit bus, isnt a limiting factor is cause there isnt 1 gig of ddr4, its only 512 A very small performance diffrence will be seen. If it were ddr3 than there would be no bottle neck on the memory bus.

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003

At stock speeds, yes. Clock for clock, no.

Clock for clock, the 2900pro/xt has exactly the same pixel fillrate, texture fillrate and shader processing power as the 3870. The ONLY difference is that the 3870 has significantly lower memory bandwidth.

Now if the 3870 is still pulling ahead clock for clock (which it hasn't) then there would definitely be something fishy going on because performance wise they are the exact same architecture.

edit:
here is a good comparison of the two using the crysis hotfix driver:
http://www.extremetech.com/article2/...2219904,00.asp

That is an extremely unbiased website.