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
Cypress: What’s New
With our refresher out of the way, let’s discuss what’s new in Cypress.
Starting at the SPU level, AMD has added a number of new hardware instructions to the SPUs and sped up the execution of other instruction, both in order to improve performance and to meet the requirements of various APIs. Among these changes are that some dot products have been reduced to single-cycle computation when they were previously multi-cycle affairs. DirectX 11 required operations such as bit count, insert, and extract have also been added. Furthermore denormal numbers have received some much-needed attention, and can now be handled at full speed.
Perhaps the most interesting instruction added however is an instruction for Sum of Absolute Differences (SAD). SAD is an instruction of great importance in video encoding and computer vision due to its use in motion estimation, and on the RV770 the lack of a native instruction requires emulating it in no less than 12 instructions. By adding a native SAD instruction, the time to compute a SAD has been reduced to a single clock cycle, and AMD believes that it will result in a significant (>2x) speedup in video encoding.
The clincher however is that SAD not an instruction that’s part of either DirectX 11 or OpenCL, meaning DirectX programs can’t call for it, and from the perspective of OpenCL it’s an extension. However these APIs leave the hardware open to do what it wants to, so AMD’s compiler can still use the instruction, it just has to know where to use it. By identifying the aforementioned long version of a SAD in code it’s fed, the compiler can replace that code with the native SAD, offering the native SAD speedup to any program in spite of the fact that it can’t directly call the SAD. Cool, isn’t it?
Last, here is a breakdown of what a single Cypress SP can do in a single clock cycle:
- 4 32-bit FP MAD per clock
- 2 64-bit FP MUL or ADD per clock
- 1 64-bit FP MAD per clock
- 4 24-bit Int MUL or ADD per clock
- SFU : 1 32-bit FP MAD per clock
Moving up the hierarchy, the next thing we have is the SIMD. Beyond the improvements in the SPs, the L1 texture cache located here has seen an improvement in speed. It’s now capable of fetching texture data at a blistering 1TB/sec. The actual size of the L1 texture cache has stayed at 16KB. Meanwhile a separate L1 cache has been added to the SIMDs for computational work, this one measuring 8KB. Also improving the computational performance of the SIMDs is the doubling of the local data share attached to each SIMD, which is now 32KB.
At a high level, the RV770 and Cypress SIMDs look very similar
The texture units located here have also been reworked. The first of these changes are that they can now read compressed AA color buffers, to better make use of the bandwidth they have. The second change to the texture units is to improve their interpolation speed by not doing interpolation. Interpolation has been moved to the SPs (this is part of DX11’s new Pull Model) which is much faster than having the texture unit do the job. The result is that a texture unit Cypress has a greater effective fillrate than one under RV770, and this will show up under synthetic tests in particular where the load-it and forget-it nature of the tests left RV770 interpolation bound. AMD’s specifications call for 68 billion bilinear filtered texels per second, a product of the improved texture units and the improved bandwidth to them.
Finally, if we move up another level, here is where we see the cause of the majority of Cypress’s performance advantage over RV770. AMD has doubled the number of SIMDs, moving from 10 to 20. This means twice the number of SPs and twice the number of texture units; in fact just about every statistic that has doubled between RV770 and Cypress is a result of doubling the SIMDs. It’s simple in concept, but as the SIMDs contain the most important units, it’s quite effective in boosting performance.
However with twice as many SIMDs, there comes a need to feed these additional SIMDs, and to do something with their products. To achieve this, the 4 L2 caches have been doubled from 64KB to 128KB. These large L2 caches can now feed data to L1 caches at 435GB/sec, up from 384GB/sec in RV770. Along with this the global data share has been quadrupled to 64KB.
RV770 vs...
Cypress
Next up, the ROPs have been doubled in order to meet the needs of processing data from all of those SIMDs. This brings Cypress to 32 ROPs. The ROPs themselves have also been slightly enhanced to improve their performance; they can now perform fast color clears, as it turns out some games were doing this hundreds of times between frames. They are also responsible for handling some aspects of AMD’s re-introduced Supersampling Anti-Aliasing mode, which we will get to later.
Last, but certainly not least, we have the changes to what AMD calls the “graphics engine”, primarily to bring it into compliance with DX11. RV770’s greatly underutilized tessellator has been upgraded to full DX11 compliance, giving it Hull Shader and Domain Shader capabilities, along with using a newer algorithm to reduce tessellation artifacts. A second rasterizer has also been added, ostensibly to feed the beast that is the 20 SIMDs.
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SiliconDoc - Thursday, September 24, 2009 - link
Oh really ? Now wait a minute, spin master. When the site here whined about "paper launch" it was Derek who brought up a two or three year old nvidia card, and cried and whined about it. Then speculated the GTX275 was paper, and then "a phantom card".Well, that didn't happen.... no apologies about it ever either.
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The PAPER launches of late are ATI ATI ATI ! ! !
We have the 4770, and now this one !
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Gee, when ATI BLOWS IT, we suddenly talk in vague terms about "the companies" having "papery launches" as " the general rule of thumb of how it's done.." - and that makes us "not a fan boy!??!"
R0FLMAO !!!!
Yes, of course, since the red ati is bleeding paper launches and the last one from nvidia one can actually cite is YEARS AND YEARS ago, yes, of course, you're correct, it's "unnamed companies in the multiple" that "do it"....
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I swear to god, I cannot even believe the massive brainwashing that is a gigantic pall all over the place.
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If I'm WRONG, please be kind, and tell me what nvidia paper launches I missed.... PLEASE LET ME KNOW.
Genx87 - Wednesday, September 23, 2009 - link
Is\was a good idea to shoot for as this is most certainly what Nvidia is going to attempt to achieve. But I am a bit disappointed this care rarely achieved it.I do like angle independent AF though. Should be interesting to see what Nvidia brings to the table. But kind of like the CPU situation(i5) I am kind of meh. But will say this has more potential compared to its predecessor than the i5 series does compared to Core 2 Duo.
SiliconDoc - Wednesday, September 23, 2009 - link
I thought that was just great, those pretty pictures, and then I get to reading. I see the 4890 and SQUARES. I see the GTX285, with CIRCLES and an outer rounded octagon.Then the 5870- and it's "perfectly round" angle independent algorithm, but I still see some distortions.
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So I get to reading and am told "the 4890 and 285 are virtually the same". I guess the wheel was first made square, and rolled as well as when it became round. No chance the reviewer could tell the truth and remark that NVidia has the best, until today.. NOPE can't do that!
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Then, of course, the celebration for the "perfection" of the 5870 and ATI's superb success in the "round" category...
EXCEPT:
We get to the actual implementations and NO PERCIEVED DIFFERENCE IS VISUALLY THERE. It cannot be seen. The article even states they searched in vain for some game to show the difference. LOL
All that extra effort to for pete sakes show that ATI superiority...all WASTED EFFORT, but for red roosters I'm certain it was a very exciting quest, titillating, gee a change to take down big green...
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So bottom line is IT'S A BIG FAT ZERO, even the older, worse ati implementation is apparently "non distinguishable".
It is remarked that NVidia doesn't "officially" support this method in game, and of course, after much red rooster effort, one finds out why.
THERE IS NO DIFFERENCE in visual quality. Another phantom red "win".
Another reason NVidia makes money (why waste it on worthless crap in developement that makes no difference), while ATI does not.
Yeah, that was so cool.
So happy the "mental ideation of perfection in the card for ati fans" was furthered. ROFL
Dante80 - Wednesday, September 23, 2009 - link
A quick question. Why is there no 5850 review available atm?1> Was there a separate NDA for the 2 cards?
2> Were there no sample cards given by AMD to reviewers?
3> Did AMD ask reviewers to postpone said reviews due to market supply problems/glitches?
4> Was this a strategy decision by AMD, for marketing or other reasons?
Ryan Smith - Wednesday, September 23, 2009 - link
AMD only provided us with 2 5870s, the 5850 was not sampled. 5800 series cards are in short supply, even for reviewers.Dante80 - Thursday, September 24, 2009 - link
Thank you for the prompt answer, that was what I was guessing too. Cheers...^^Spoelie - Wednesday, September 23, 2009 - link
To get enough 5870 cards in the channel for a hard launch, they used every possible die.There are probably not enough harvested dies to create the 5850 line just yet. And they're not gonna use fully functional ones that can go in a 5870 when supply for them is tight already.
Once the 5850 is launched, demand for them is up and yields matured, they'll have to use fully functional dies to keep supply up, but now they're building up inventory for a hard launch during the coming weeks.
SiliconDoc - Wednesday, September 23, 2009 - link
Uhh, just a minute there feller. The SOFT or PAPER LAUNCH has already hit, the big LAUNCH DATE is today....Newegg is a big ZERO available... (one Powercolor was there 30 mins ago, the other 3 listed are NOT avaailable, I watched them appear last night).
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So, when Ati has a "hard launch" they get "many weeks after the launch date" to "ramp up production" and "fill the need".
ROFLMAO
I was here when this site and the red roosters whined about Nvidia and appear launches, and I believe it was the GTX275 that was predicted to be PAPER (not very long ago in fact) here, and the article EVEN SPECULATED IT WAS A PHANTOM CARD.
All the red roosters piled on, but.... the card was available on launch, it wasn't a PHANTOM, and all that bs was quickly forgotten and shoved into the memory hole like it never happened...
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Oh, but when it's ATI and not Nvidia, the 4770 can remain almost pure paper near forever, and this one, golly it can be 95% paper and it's just " getting ready for a hard launch" WEEKS BEYONDS the launch date!
ROFLMAO
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No bias here?!? "Where's da' bias?!?!" said the red rooster (to the green goblin)...
Give me a break.
chrnochime - Friday, September 25, 2009 - link
Just because you can't find it in the states doesn't mean it's a fake launch. And fake launch? What are you a 12 year old or something? You're like the nvidia version of snakeoil. Just go play with your nvidia part m'kay ?SiliconDoc - Sunday, September 27, 2009 - link
Well, since you insulted, and mischaracterized, I came across the reminder about the 4870 paper launch.Yes, that's correct, this is how ATI rolls, a big fat lying launch date, a piddle of a few cards, then wait a couple weeks or a month.
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" The cards are fast, but as many pointed out HD 5870 is not faster than Geforce GTX 295, which is something that many have expected. Radeon 5850 will also start selling in October time, but remember, last summer when ATI launched 4870, the card was almost impossible to buy and weeks if not months after, the availability finally improved. "
http://www.fudzilla.com/content/view/15643/1/">http://www.fudzilla.com/content/view/15643/1/
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Like I've kept saying, the bias is so bad... I keep discovering more big fat ati blunderous moves, that are instead ascribed to imaginarily to Nvida.
Thanks for the incorrect whining, anger, and standard PC e-mindless chatroom repeated, non original, heard ten thousand times, brainless insult, it actually helped me.
I learned ATI blew their 4870 launch with paper lies as well.
You're a great help friend.