ATI Radeon R600

R600 Technical Aspects

Techinical Aspects

Now onto the Technical bits that make up the r600. As I said earlier this is going to be a brief run-through and not a University dissertation on r600.

Unified Shader Architecture

The R600's design is similar to the xbox360's GPU as it is based on the Unified Superscalar shader architecture.

The Unified Shader Architecture coupled with Microsofts new DirectX 10 API allows the shaders to be 'unified'.
What this means is that instead of having a fixed number of shaders assigned to certain tasks, (eg x1900: 8 vertex shader processors & 48 pixel shader processors) they can be assigned depending on the job at hand meaning all of the shaders are used.

As a result, the GPU will be fully utilised and therefore performance will be enhanced, gaining up to 25% in performance.

Unified Superscalar Shader Architecture

  • 320 stream processing units
    • Dynamic load balancing and resource allocation for vertex, geometry, and pixel shaders
    • Common instruction set and texture unit access supported for all types of shaders
    • Dedicated branch execution units and texture address processors
  • 128-bit floating point precision for all operations
  • Command processor for reduced CPU overhead
  • Shader instruction and constant caches
  • Up to 80 texture fetches per clock cycle
  • Up to 128 textures per pixel
  • Fully associative multi-level texture cache design
  • DXTC and 3Dc+ texture compression
  • High resolution texture support (up to 8192 x 8192)
  • Fully associative texture Z/stencil cache designs
  • Double-sided hierarchical Z/stencil buffer
  • Early Z test, Re-Z, Z Range optimization, and Fast Z Clear
  • Lossless Z & stencil compression (up to 128:1)
  • Lossless color compression (up to 8:1)
  • 8 render targets (MRTs) with anti-aliasing support
  • Physics processing support

Now I don't need to say that the 2X00 series support DX10 fully with full SM 4.0 support. This is ATI's first card supporting the new Microsoft API and they've followed their Xenos Xbox 360 chip in making r600. In saying that, r600 has taken Xenos that bit futher and gone with a completely unified shader architecture, something nVidia have also done with G80.

The r600 consists of 320 independent stream processing units, made up of 64 superscaler shader processors, each a five-way unit. These all support FP32 bit precision in mathematical operations. Added in are 16 texture units (TMU's) and 16 ROPs (render backends). The 2900 XT has a 512mb ring-bus architecture, taken forward from r580, which can break through 100BG/sec; the same as the G80 can, but at a more interesting price-point.

ATI have also added a "programmable tessellation unit". This is notable as the current DX10 specification do not include this, although Microsoft is said to have plans in including it at a later stage.

Shader Units

ATI have gone a different router to nVidia in as far as their Shader Units are concerned. This isn't in so much as the actual number (though they do differ), more the approach to the way that each stream processor is layed out. r600 uses a 5-way superscaler shader processor, with 5 parts and 5 instructions per clock. These sit in clusters of 16 shaders (80 stream processing units each cluster altogether) and added to them is a branch execution unit. Added is a 64KB memory read/write cache which can be accessed by any shader cluster. This means that in DX10 architecture you can avoid going through the render backend and write straight to memory.

r600 shader

So that's the big difference in architecture of the stream processing units as I see it. ATI have added a lot of additional features, but as this is a brief article, I will leave you to click on the links I have provided below for a more in-depth analysis of the architecture. Now onto what some of this means.
«Prev 1 2 3 4 5 Next»

Most Recent Comments

16-05-2007, 14:00:16


The long awaited and hugely anticipated ATI card is finally here. We have been given access to information and media documenting ATI's first DirectX10 graphics card. The technical specifications look promising, with some features never before seen on a GPU, making these cards innovative and one of a kind.

This article is designed to run through a little bit of the technical information without confusing the hell out of you. It is a short and sweet introduction into r600 and it's architecture and is meant to cover it in an understandable way.

I've just finished my first article (with the help of Kempez) for OC3D. I hope people find it interesting and informative.

Please Discuss Quote

16-05-2007, 14:03:07

Great work mate. Nice and simple and easy to understand while getting the key points across

Hope everyone enjoys reading it Quote

16-05-2007, 15:00:09

Great article, cant wait for the review.


16-05-2007, 16:09:29

Good work on your first write up matey!

Once again I cannot wait for the view, equk.. are you doing the review too?Quote

16-05-2007, 16:32:16

No I'm doing that Quote

16-05-2007, 16:35:56

Originally Posted by name='Kempez'
No I'm doing that

Suprise suprise.. Kemp always gets his hands on the best stuff!

Good on ya mate!Quote

16-05-2007, 16:37:28

top banana!Quote

16-05-2007, 17:57:19

PP Mguire
Well written review. I enjoyed reading it.Quote

16-05-2007, 18:23:50

A good read, seems like ATI/AMD are really pushing the envelope with sound, Avivo etc.

Two things caught my eye though, at the bottom of page 4 it says.

ATI have talked about the ring-bus architecture before, but this time they've given their card 512mb to play with - a worlds first.

I think you mean 512 bits, maybe?

At the top of page 5 it says.

However if your an HTPC enthusiast you are going to have a decent discrete GPU for your audio so I see the 5.1 sound card as a pretty neat if not slightly useless addition to the 2X00 series.

Do you maybe mean discrete sound card?

I look forward to your next article. Quote

16-05-2007, 18:36:31

Yep my bad - should be bit and APU (probably just sound card is better)Quote

16-05-2007, 19:51:18

Thanks for the feedback

I think the onchip sound is good & means ATI can market it a bit better, saying it's one of a kind, while also gaining conformity for both protected content and also Windows Vista Premium Logo.

Originally Posted by name='equk'
Because the video and sound are not seperated the card conforms to the protected content output path, which also makes it compliant with Windows Vista Premium Logo requirements.
Originally Posted by name='kempez'
However if your an HTPC enthusiast you are going to have a decent discrete GPU for your audio so I see the 5.1 sound card as a pretty neat if not slightly useless addition to the 2X00 series.
Altho I agree with what kempez has said, most people do already have a dedicated soundcard, all the on-chip one means tho is you don't need loads of wires and it can connect direct to new HDMI tv's.Quote

16-05-2007, 20:04:39

Ye I get where you're going but it's not a premium audio chip which is a little disappointingQuote

Register for the OC3D Newsletter

Subscribing to the OC3D newsletter will keep you up-to-date on the latest technology reviews, competitions and goings-on at Overclock3D. We won't share your email address with ANYONE, and we will only email you with updates on site news, reviews, and competitions and you can unsubscribe easily at any time.

Simply enter your name and email address into the box below and be sure to click on the links in the confirmation emails that will arrive in your e-mail shortly after to complete the registration.

If you run into any problems, just drop us a message on the forums.