DX10 Redux

Being late to the game also means being late to DirectX 10; luckily for AMD there hasn't been much in the way of DX10 titles released nor will there be for a while - a couple titles should have at least some form of DX10 support in the next month or two, but that's about it. What does DX10 offer above and beyond DX9 that makes this move so critical? We looked at DirectX 10 in great detail when NVIDIA released G80, but we'll give you a quick recap here as a reminder of what the new transistors in R600 are going to be used for.

From a pure performance standpoint, DX10 offers more efficient state and object management than DX9, resulting in less overhead from the API itself. There's more room to store data for use in shader programs, and this is largely responsible for the reduction in management overhead. For more complex shader programs, DX10 should perform better than DX9.

A hot topic these days in the CPU world is virtualization, and although it's not as much of a buzzword among GPU makers there's still a lot to talk about the big V when it comes to graphics. DirectX 10 and the new WDDM (Windows Display Driver Model) require that graphics hardware supports virtualization, the reason being that DX10 applications are no longer guaranteed exclusive access to the GPU. The GPU and its resources could be split between a 3D game and physics processing, or in the case of a truly virtualized software setup, multiple OSes could be vying for use of the GPU.

Virtual memory is also required by DX10, meaning that the GPU can now page data out to system memory if it runs out of memory on the graphics card. If managed properly and with good caching algorithms, virtualized graphics memory can allow game developers to use ridiculously large textures and objects. 3DLabs actually first introduced virtualized graphics memory on its P10 graphics processor back in 2002; Epic Games' Tim Sweeney had this to say about virtual memory for graphics cards back then:

"This is something Carmack and I have been pushing 3D card makers to implement for a very long time. Basically it enables us to use far more textures than we currently can. You won't see immediate improvements with current games, because games always avoid using more textures than fit in video memory, otherwise you get into texture swapping and performance becomes totally unacceptable. Virtual texturing makes swapping performance acceptable, because only the blocks of texels that are actually rendered are transferred to video memory, on demand.

Then video memory starts to look like a cache, and you can get away with less of it - typically you only need enough to hold the frame buffer, back buffer, and the blocks of texels that are rendered in the current scene, as opposed to all the textures in memory. So this should let IHVs include less video RAM without losing performance, and therefore faster RAM at less cost.

This does for rendering what virtual memory did for operating systems: it eliminates the hard-coded limitation on RAM (from the application's point of view.)"

Obviously the P10 was well ahead of its time as a gaming GPU, but now with DX10 requiring it, virtualized graphics memory is a dream come true for game developers and will bring even better looking games to DX10 GPUs down the line. Of course, with many GPUs now including 512MB or more RAM it may not be as critical a factor as before, at least until we start seeing games and systems that benefit from multiple Gigabytes of RAM.

Continuing on the holy quest of finding the perfect 3D graphics API, DX10 does away with the hardware capability bits that were present in DX9. All DX10 hardware must support the same features and furthermore, Microsoft will only allow DX10 shaders to be written in HLSL (High Level Shader Language). The hope is that the combination of eliminating cap bits and shader level assembly optimization will prevent any truly "bad" DX10 hardware/software from getting out there, similar to what happened in the NV30 days.

Although not specifically a requirement of DX10, Unified Shaders are a result of changes to the API. While DX9 called for different precision for vertex and pixel shaders, DX10 requires all shaders to use 32-bit precision, making the argument for unified shader hardware more appealing. With the same set of 32-bit execution hardware, you can now run pixel, vertex, and the new geometry shaders (also introduced in DX10). Unified shaders allow extracting greater efficiency out of the hardware, and although they aren't required by DX10 they are a welcome result now implemented by both major GPU makers.

Finally, there are a number of enhancements to Shader Model 4.0 which simply allow for more robust shader programs and greater programmer flexibility. In the end, the move to DX10 is just as significant as prior DirectX revisions but don't expect this rate of improvement to continue. All indications point to future DX revisions slowing in their pace and scope. However, none of this matters to us today; with the R600 as AMD's first DX10 architecture, much has changed since the DX9 Radeon X1900 series.

Index R600 Overview
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  • TA152H - Monday, May 14, 2007 - link

    Fanboy? What a dork.

    I've had success with ATI, not with NVIDIA, and I know ATI stuff a lot better so it's just easier for me to work with. It's not an irrational like or dislike. I bought one NVIDIA and it was a nightmare. Plus, I'm not as sure they'll be around for very long as I am ATI/AMD, although they had a good quarter, and AMD surely had a dreadful one.

    Selling discrete video cards alone might get a lot more difficult with the integration of CPUs, and GPUs.
    Reply
  • yyrkoon - Monday, May 14, 2007 - link

    You are a fanboy, face it. 'I tried a nVidia card once . . .' How long ago was that ? Who made the card ? Did you have it configured properly? Once?! Details like this are important, and seemily/conviently left out. Anyhow, anyone claiming that nVIdia cards are 'junk' has definate issues with assembling/configuring hardware. I say this because my current system uses a nVidia based card, and is 100% rock solid. 'Person between the chair and keyboard' rings a bell.

    Ask any Linux user why they refuse to use ATI cards in their system . . . You are also one of these people out there that claims ATI driver support is superior to nVIdias driver support I suppose ? If you have truely been using ATI products for 20 years, then you know ATI has one of the worst reputations on the planet for driver support(and while it may have improved, it is not as good as nVidias still).

    Yeah, anyhow, ATI, and nVidia both can have problems with their hardware, it is not based 100% on their architecture, but the OEM releasing the products have a lot of effect here also. There are bad OEMs to buy from here on both sides of the fence, knowing who to stay away from, is half the work when building a PC, and probably had a lot more to do with your alleged 'bad nVIdia card', assuming you actually configured the card properly.

    I also had a problem with an nVIdia card once, I bought a brand new GF3 card about 7 years ago, and a few of the older games I had, would not display properly with it. What did I do ? I waited about a month, for a new driver, and the problem was solved. I have also had issues with ATI cards, one of which drew too much power from the AGP slot, and would cause the given system to crash 1-2 times a day. This was a design issue/oversight on ATI's behalf(the card was made by Saphire, who also makes ATIs cards). What did I do ? I replaced the card with an nVIdia card, and the system has been stable since.

    So you see, I too can skew things to make anyone look bad also, and in the end, it would only serve to make me look like the dork. But if you want to pay more, for less, that is perfectly fine by me.
    Reply
  • Pirks - Monday, May 14, 2007 - link

    I've got all problems and crappy drivers (especially Linux ones) only from ATI while nVidia software was always much better in my experience. power hungry noisy monsters made by whom? by ATI! as always :) same shit as with their x1800/x1900 miserable power guzzling series

    discrete video cards are not going away any time soon. ever heard of integrated video used in games, besides ones from 2000, like old Quake 2? no? then please continue your lovefest with ATI, but for me - it looks like I'll pass on them this time again - since Radeon 9800Pro they went downhill and continue in that direction. they MAY make a decent integrated CPU/GPU budget-oriented vendor in a future, for all those office folks playing simple 2D office games, but real stuff? nope, ATI is still out of the game for me. let's see if they manage to come back with reincarnation of R300 in future.

    ironically, AMD CPUs on the other hand have best price/performance ratio, so intel won't see me as their customer. I wish ATI 3D chips were as good as AMD CPUs in that regard (and overclockers please shut up, I'm not bothering to OC my rig because I don't enjoy benchmark numbers, I enjoy REAL stuff like games, and Intel is out of the game for me as well, at least until their budget single core Conroes are out)
    Reply
  • utube545 - Tuesday, May 22, 2007 - link

    Get a clue, you fucking cretin. Reply
  • dragonsqrrl - Thursday, August 25, 2011 - link

    haha... lol, wow. facepalm. Reply
  • dragonsqrrl - Thursday, August 25, 2011 - link

    Damn you're a fail noob of an ATI fanboy. Time has not been kind to the HD2900XT, and now you sound more ridiculous then ever... lol. Reply
  • yzkbug - Monday, May 14, 2007 - link

    Not a word about new AVIVO HD and digital sound features? Reply
  • DerekWilson - Wednesday, May 16, 2007 - link

    we mentioned this ...

    on the r600 overview page ...
    Reply
  • photoguy99 - Monday, May 14, 2007 - link

    First to be clear and I do not condone the title of this article, there's no need to bring racism into this.

    But my point is NVidia can and will react by making the performance per dollar competitive for the R600 vs 8800GTS.

    Once the prices are comparable, why buy a more power hungry part (the ATI)?

    This is one disadvantage they can't correct until the next respin.

    Reply
  • DrMrLordX - Monday, May 14, 2007 - link

    Based on the benchmarks results, the only reason I can see for getting 2900XTs is if a). you don't care about power consumption and b). want to run a Crossfire rig at a lower cost of entry than dual-8800 GTXs or 8800 Ultras.

    As others have said, some more benchmarks in mature DX10 titles might show who the real winner here is performance-wise, and that holds true for multi-GPU scenarios as well.
    Reply

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