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nVidia GeForce GTX 280 - GT200: Graphics Architecture

By Edward Chester



Our Score:


Although GT200's architecture is in many ways very similar to that of G80, there is a huge number of tweaks that have been applied to this new core that make it a considerably better whole. Before we get too far into the comparisons, though, let's get back to basics.

The following is a Streaming Multiprocessor, or SM as nVidia abbreviates it to:

As you can see from the picture, an SM is an array of processing cores called Streaming Processors (SPs), with a portion of cache memory and an instruction scheduler. There's actually a bit more to it than that, including two Special Function Units (SFU) that aren't pictured, but we won't go too far into the specifics. Essentially, this little lot acts like a mini eight core CPU with each core performing the calculations associated with a single pixel. The small (16KB) portion of memory is used to handle only the specific data associated with those eight pixels the SM is currently working on. This is the basic building block of nVidia's unified shader architecture and is the same on both the G80, G92 and GT200.

TPC from GT200

As we zoom out one step we see the first major dividing point between G80/G92 and GT200. In GT200, three of these SMs are combined to form a Texture/Processor Cluster (TPC), whereas G80 and G92 used two SMs per TPC. The principle's the same, there's just more in the new chip - 32 SPs vs. 24 on G80.

TPC from G80/G92

As well as combining the SMs, a TPC also adds texture processing capabilities and again this is another area where the new chip differs from its forebears, sort of. On G80 you got four texture address units and eight texture filtering units per TPC, with G92 the number of address units doubled to eight while filtering remained at eight units. Now, with GT200 things have, well, stayed the same.

You still get eight texture address units and eight filtering units per TPC, it's just the ratio of shaders to texturing units has changed. So, while the shader count of each TPC has increased by 50 per cent, the texturing power of each TPC has remained the same. At first this may seem like a backward step but most modern games are becoming shader dependent so the change in ratio makes sense. Moreover, when you look at the bigger picture you'll see that the total texturing power of GT200 has actually increased a small amount.


June 26, 2008, 3:33 am

"What can we say about Counter-Strike: Source that hasn't been said before? It is simply the benchmark for team-based online shooters and, four years after its release, it's still the most popular game in its genre."

I would argue against that one a quick look at www.xfire.com shows COD4 at about 9 mil, COD2 at 5 mil and CSS at 2 mil minutes played today.

Otherwise a very interesting article, the only thing it makes me sad about is the size of my wallet :)


June 26, 2008, 1:19 pm

Okay, it's obviously taken a hit in recent years. I'll amend that line. still doing damn well for such an old game, though.


June 27, 2008, 6:20 am

Well call of duty is a full production game. with single player mode and many different versions of multi player... Cs is A Mod it is not a stand alone game. And there is only one mode of play (i.e. there is no capture the flag or free for all modes)


June 27, 2008, 7:17 pm

Sorry, I'm not sure what your point is Intex?


June 27, 2008, 11:16 pm

I thought this was a fantastic review Ed, very in-depth and informative. Looking forward to a GTX260 review, as there is no way I'm shelling out 400 quid on a graphics card! The 260s seem to be going for 𧶲-300 at the moment... which is still very high in my book, but tempting given the potential performance gains over my current 7900GT KO.

P.S. Ed - I think Intex was replying to Exitialis, justifying the currently lower usage stats of CS:S.

Varis Vitols

July 3, 2008, 4:25 pm

life said on 27th June 2008

In that case, why don't You have a look at Radeon HD 4870? It outperforms GTX 260 in almost every case, particularly with AA enabled - by 20 percent. In many cases it stands very close to GTX 280, with AA enabled, but costs only 185-230 pounds at online stores, depending on manufacturer.


July 3, 2008, 11:43 pm

What are your comments on the explosive heat and noise that the GTX 280 generates?

Flight Instructor

March 27, 2009, 6:49 pm

I like your reviews, in particular when they refer to games hardware, but I only use flight simulator, is it possible to include this type of game when reviewing hardware.

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