AMD's Radeon HD 5870: Bringing About the Next Generation Of GPUs
by Ryan Smith on September 23, 2009 9:00 AM EST- Posted in
- GPUs
DirectX11 Redux
With the launch of the 5800 series, AMD is quite proud of the position they’re in. They have a DX11 card launching a month before DX11 is dropped on to consumers in the form of Win7, and the slower timing of NVIDIA means that AMD has had silicon ready far sooner. This puts AMD in the position of Cypress being the de facto hardware implementation of DX11, a situation that is helpful for the company in the long term as game development will need to begin on solely their hardware (and programmed against AMD’s advantages and quirks) until such a time that NVIDIA’s hardware is ready. This is not a position that AMD has enjoyed since 2002 with the Radeon 9700 and DirectX 9.0, as DirectX 10 was anchored by NVIDIA due in large part to AMD’s late hardware.
As we have already covered DirectX 11 in-depth with our first look at the standard nearly a year ago, this is going to be a recap of what DX11 is bringing to the table. If you’d like to get the entire inside story, please see our in-depth DirectX 11 article.
DirectX 11, as we have previously mentioned, is a pure superset of DirectX 10. Rather than being the massive overhaul of DirectX that DX10 was compared to DX9, DX11 builds off of DX10 without throwing away the old ways. The result of this is easy to see in the hardware of the 5870, where as features were added to the Direct3D pipeline, they were added to the RV770 pipeline in its transformation into Cypress.
New to the Direct3D pipeline for DirectX 11 is the tessellation system, which is divided up into 3 parts, and the Computer Shader. Starting at the very top of the tessellation stack, we have the Hull Shader. The Hull Shader is responsible for taking in patches and control points (tessellation directions), to prepare a piece of geometry to be tessellated.
Next up is the tesselator proper, which is a rather significant piece of fixed function hardware. The tesselator’s sole job is to take geometry and to break it up into more complex portions, in effect creating additional geometric detail from where there was none. As setting up geometry at the start of the graphics pipeline is comparatively expensive, this is a very cool hack to get more geometric detail out of an object without the need to fully deal with what amounts to “eye candy” polygons.
As the tesselator is not programmable, it simply tessellates whatever it is fed. This is what makes the Hull Shader so important, as it’s serves as the programmable input side of the tesselator.
Once the tesselator is done, it hands its work off to the Domain Shader, along with the Hull Shader handing off its original inputs to the Domain Shader too. The Domain Shader is responsible for any further manipulations of the tessellated data that need to be made such as applying displacement maps, before passing it along to other parts of the GPU.
The tesselator is very much AMD’s baby in DX11. They’ve been playing with tesselators as early as 2001, only for them to never gain traction on the PC. The tesselator has seen use in the Xbox 360 where the AMD-designed Xenos GPU has one (albeit much simpler than DX11’s), but when that same tesselator was brought over and put in the R600 and successive hardware, it was never used since it was not a part of the DirectX standard. Now that tessellation is finally part of that standard, we should expect to see it picked up and used by a large number of developers. For AMD, it’s vindication for all the work they’ve put into tessellation over the years.
The other big addition to the Direct3D pipeline is the Compute Shader, which allows for programs to access the hardware of a GPU and treat it like a regular data processor rather than a graphical rendering processor. The Compute Shader is open for use by games and non-games alike, although when it’s used outside of the Direct3D pipeline it’s usually referred to as DirectCompute rather than the Compute Shader.
For its use in games, the big thing AMD is pushing right now is Order Independent Transparency, which uses the Compute Shader to sort transparent textures in a single pass so that they are rendered in the correct order. This isn’t something that was previously impossible using other methods (e.g. pixel shaders), but using the Compute Shader is much faster.
Other features finding their way into Direct3D include some significant changes for textures, in the name of improving image quality. Texture sizes are being bumped up to 16K x 16K (that’s a 256MP texture) which for all practical purposes means that textures can be of an unlimited size given that you’ll run out of video memory before being able to utilize such a large texture.
The other change to textures is the addition of two new texture compression schemes, BC6H and BC7. These new texture compression schemes are another one of AMD’s pet projects, as they are the ones to develop them and push for their inclusion in DX11. BC6H is the first texture compression method dedicated for use in compressing HDR textures, which previously compressed very poorly using even less-lossy schemes like BC3/DXT5. It can compress textures at a lossy 6:1 ratio. Meanwhile BC7 is for use with regular textures, and is billed as a replacement for BC3/DXT5. It has the same 3:1 compression ratio for RGB textures.
We’re actually rather excited about these new texture compression schemes, as better ways to compress textures directly leads to better texture quality. Compressing HDR textures allows for larger/better textures due to the space saved, and using BC7 in place of BC3 is an outright quality improvement in the same amount of space, given an appropriate texture. Better compression and tessellation stand to be the biggest benefactors towards improving the base image quality of games by leading to better textures and better geometry.
We had been hoping to supply some examples of these new texture compression methods in action with real textures, but we have not been able to secure the necessary samples in time. In the meantime we have Microsoft’s examples from GameFest 2008, which drive the point home well enough in spite of being synthetic.
Moving beyond the Direct3D pipeline, the next big feature coming in DirectX 11 is better support for multithreading. By allowing multiple threads to simultaneously create resources, manage states, and issue draw commands, it will no longer be necessary to have a single thread do all of this heavy lifting. As this is an optimization focused on better utilizing the CPU, it stands that graphics performance in GPU-limited situations stands to gain little. Rather this is going to help the CPU in CPU-limited situations better utilize the graphics hardware. Technically this feature does not require DX11 hardware support (it’s a high-level construct available for use with DX10/10.1 cards too) but it’s still a significant technology being introduced with DX11.
Last but not least, DX11 is bringing with it High Level Shader Language 5.0, which in turn is bringing several new instructions that are primarily focused on speeding up common tasks, and some new features that make it more C-like. Classes and interfaces will make an appearance here, which will make shader code development easier by allowing for easier segmentation of code. This will go hand-in-hand with dynamic shader linkage, which helps to clean up code by only linking in shader code suitable for the target device, taking the management of that task out of the hands of the coder.
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avaughan - Wednesday, September 23, 2009 - link
Ryan,When you review the 5850 can you please specify memory size for all the comparison cards. At a guess the GTS 250 had 1GB and the 9800GT had 512 ?
Thanks
ThePooBurner - Wednesday, September 23, 2009 - link
With a full double the power and transistors and everything else including optimizations that should get more band for buck out of each one of those, why are we not seeing a full double the performance in games compared to the previous generation of cards?SiliconDoc - Wednesday, September 23, 2009 - link
Umm, because if you actually look at the charts, it's not "double everything".In fact, it's not double THE MOST IMPORTANT THING, bandwidth.
For pete sakes an OC'ed GTX260 core 192 get's to 154+ bandwidth rather easily, surpassing the 153.6 of ati's latest and greatest.
So, you have barely increased ram speed, same bus width... and the transistors on die are used up in "SHADERS" and ROPS....etc.
Where is all that extra shader processing going to go ?
Well, it goes to SSAA useage for instance, which provides ZERO visual quality improvement.
So, it goes to "cranking up the eye candy settings" at "not a very big framerate improvement".
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So they just have to have a 384 or a 512 bus they are holding back. I dearly hope so.
They've already been losing a BILLION a year for 3+ years in a row, so the cost excuse is VERY VERY LAME.
I mean go check out the nvidia leaked stats, they've been all over for months - DDR5 and a 512 bit, with Multiple IMD, instead of the 5870 Single IMD.
If you want DOUBLE the performance wait for Nvidia. From DDR3 to DDR5, like going from 4850 to 4890, AND they (NVIDIA) have a whole new multiple instruction super whomp coming down the pike that is never done before, on their hated "gigantic brute force cores" (even bigger in the 40nm shrink -lol) that generally run 24C to 15C cooler than ati's electromigration heat generators.
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So I mean add it up. Moving to DDR5, moving to multiple data, moving to 40nm, moving with 512 bit bus and AWESOME bandwidth, and the core is even bigger than the hated monster GT200. LOL
We're talking EPIC palmface.
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In closing, buh bye ati !
silverblue - Thursday, September 24, 2009 - link
Let's wait for GT300 before we make any sweeping generalisations. The proof is in the pudding and it won't be long before we see it.And don't let the door hit you on the way out.
SiliconDoc - Thursday, September 24, 2009 - link
Oh mister, if we're waiting, that means NO BUYING the 5870, WAIT instead.Oh, yeah, no worries, it's not available.
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Now, when my statements prove to be true, and your little crybaby snark with NO FACTS used for rebuttal are proven to be wasted stupidity, WILL YOU LEAVE AS YOU STATED YOU WANT ME TO ?
That's what I want to know. I want to know if your little wish applies to YOU.
Come on, I'll even accept a challenge on it. If I turn out to be wrong, I leave, if not you're gone.
If I'm correct, anyone waiting because of what I've pointed out, has been given an immense helping hand.
Which BY THE WAY, the entire article FAILED TO POINT OUT, because the red love goes so deep here.
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But, you, the little red rooster ati fanner, wants me out.
ROFL - you people are JUST INCREDIBLE, it is absolutely incredible the crap you pull.
NOW, LET US KNOW WHAT LEAKED NVIDIA STATS I GOT INCORRECT WON'T YOU!?
No of course you won't !
silverblue - Friday, September 25, 2009 - link
Another problem I have with people like you is the unerring desire to rant and rave without reading things through. I said wait for GT300 before doing a proper comparison. Have you already forgotten the mess that was NV30? Paper specs do not necessarily equal reality. When the GT300 is properly previewed, even with an NDA in place, we can all judge for ourselves. People have a choice to buy what they like regardless of what you or I say.I'm not an ATI fanboy. I expended plenty of thought on what parts to get when I upgraded a few months back and that didn't just include CPU but motherboard and graphics. I was very close to getting a higher end Core2 Duo along with an nVidia graphics card; at the very least I considered an nVidia graphics card even when I decided on an AMD CPU and motherboard. In the end I felt I was getting better value by choosing an ATI solution. Doesn't make me a fanboy just because my money didn't end up on the nVidia balance sheet.
I'll take back the little comment about letting the door hit you on the way out. It wasn't designed to tell you to go away and not come back again, so my bad. I was annoyed at your ability to just attack a specific brand without any apparent form of objectivity. If you hate ATI, then you hate ATI, but do we really need to hear it all the time?
If the information you've posted about the GT300 is indeed accurate and comparable to what we've been told about the 58x0 series, then that's great, but you're going to need to lay it out in a more structured format so people can digest it more readily, as well as lay off the constant anti-ATI stance because appearing biased is not going to make people more receptive to your viewpoint. I remain sceptical that your leaked specs will end up being correct but in the end, GT300 is on its way and it'll be a monster regardless of whatever information you've posted here. I'm not going to pretend I know anything technical about GT300, but you must realise that what you've essentially done in this article is slate a working, existing product line that is being distributed to vendors as we speak in a manner that's much slower than ATI had intended yet you're attacking people for being interested in it over the GT300 which hasn't been reviewed yet, partly because you think the product is vapourware (which isn't really the case as people are getting hold of the 5870 but at a lower rate than ATI would like). Some people will choose to wait, some people will jump on the 58x0 bandwagon right now, but it's not for you to decide for them what they should buy.
Now relax, you're going to have a heart attack.
SiliconDoc - Wednesday, September 30, 2009 - link
What a LOAD OF CRAP.I don't have to outline anything, remember, ALL YOU PEOPLE cARE ABOUT IS GAMING FRAMERATE.
And that at "your price point" that doesn't include "the NVIDIA BALANCE SHEET". - which io of course, the STRANGEST WAY for a reddie to put it.
YOU JUST WANT ME TO SHUT UP. YOU DON'T WANT IT SAID. WE'LL I'M SAYING IT AGAIN, AND YOU FAILED TO ACCEPT MY CHALLENGE BECAUSE YOU'RE A CHICKEN, AND CENSOR !
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Oh, do we have to hear it... blah blah blah blah...
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YES SINCE THIS VERY ARTICEL WAS ABSOLUTELY IRRESPONSIBLE IN NOT PROPERLY ASSESSING THE COMPETITION.
CarrellK - Wednesday, September 23, 2009 - link
If a game ran almost entirely on the GPU, the scaling would be more of what you expect. You can put in a new GPU, but the CPU is no faster, main memory is no faster of bigger, the hard disk is no faster, PCIE is no faster, etc.The game code itself also limits scaling. For example the texture size can exceed the card's memory footprint, which results in performance sapping texture swaps. Each game introduces different bottlenecks (we can't solve them all).
We do our best to get linear scaling, but the fact is that we address less than a third of the game ecosystem. That we do better than 33% out of a possible 100% improvement is I think a testimony to our engineers.
BlackbirdCaD - Wednesday, September 23, 2009 - link
Why no load temp of 5870 in Crossfire??Load temp is much more important than idle temp.
There is lots of uninteresting stuff like soundlevel at idle with 5870 in crossfire, but the MOST IMPORTANT is missing: load temp with 5870 in crossfire.
SiliconDoc - Wednesday, September 23, 2009 - link
I just pulled up the chart on the 4870 CF, and although the 4870x2 was low 400's on load system power useage, the 4870 CF was 722 watts !So, I think your question may have some validity. I do believe the cards get a bit hotter in CF, and then you have the extra items on the PCB, the second slot used, the extra ram via the full amount on each card - all that adds up to more power useage, more heat in the case, and higher temps communicating with eachother. (resends for data on bus puases waitings, etc. ).
So there is something to your question.
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Other than all that the basic answer is "red fan review site".
The ATI cards are HOTTER than the nvidia under load as a very, very wide general statement, that covers almost every card they both make, with FEW exceptions.