The Radeon HD 4850 & 4870: AMD Wins at $199 and $299
by Anand Lal Shimpi & Derek Wilson on June 25, 2008 12:00 AM EST- Posted in
- GPUs
Wrapping Up the Architecture and Efficiency Discussion
Engineering is all about tradeoffs and balance. The choice to increase capability in one area may decrease capability in another. The addition of a feature may not be worth the cost of including it. In the worst case, as Intel found with NetBurst, an architecture may inherently flawed and a starting over down an entirely different path might be the best solution.
We are at a point where there are quite a number of similarities between NVIDIA and AMD hardware. They both require maintaining a huge number of threads in flight to hide memory and instruction latency. They both manage threads in large blocks of threads that share context. Caching, coalescing memory reads and writes, and handling resource allocation need to be carefully managed in order to keep the execution units fed. Both GT200 and RV770 execute branches via dynamic predication of direction a thread does not branch (meaning if a thread in a warp or wavefront branches differently from others, all threads in that group must execute both code paths). Both share instruction and constant caches across hardware that is SIMD in nature servicing multiple threads in one context in order to effect hardware that fits the SPMD (single program multiple data) programming model.
But the hearts of GT200 and RV770, the SPA (Steaming Processor Array) and the DPP (Data Parallel Processing) Array, respectively, are quite different. The explicitly scalar one operation per thread at a time approach that NVIDIA has taken is quite different from the 5 wide VLIW approach AMD has packed into their architecture. Both of them are SIMD in nature, but NVIDIA is more like S(operation)MD and AMD is S(VLIW)MD.
AMD's RV770, all built up and pretty
Filling the execution units of each to capacity is a challenge but looks to be more consistent on NVIDIA hardware, while in the cases where AMD hardware is used effectively (like Bioshock) we see that RV770 surpasses GTX 280 in not only performance but power efficiency as well. Area efficiency is completely owned by AMD, which means that their cost for performance delivered is lower than NVIDIA's (in terms of manufacturing -- R&D is a whole other story) since smaller ICs mean cheaper to produce parts.
NVIDIA's GT200, in all its daunting glory
While shader/kernel length isn't as important on GT200 (except that the ratio of FP and especially multiply-add operations to other code needs to be high to extract high levels of performance), longer programs are easier for AMD's compiler to extract ILP from. Both RV770 and GT200 must balance thread issue with resource usage, but RV770 can leverage higher performance in situations where ILP can be extracted from shader/kernel code which could also help in situations where the GT200 would not be able to hide latency well.
We believe based on information found on the CUDA forums and from some of our readers that G80's SPs have about a 22 stage pipeline and that GT200 is also likely deeply piped, and while AMD has told us that their pipeline is significantly shorter than this they wouldn't tell us how long it actually is. Regardless, a shorter pipeline and the ability to execute one wavefront over multiple scheduling cycles means massive amounts of TLP isn't needed just to cover instruction latency. Yes massive amounts of TLP are needed to cover memory latency, but shader programs with lots of internal compute can also help to do this on RV770.
All of this adds up to the fact that, despite the advent of DX10 and the fact that both of these architectures are very good at executing large numbers of independent threads very quickly, getting the most out of GT200 and RV770 requires vastly different approaches in some cases. Long shaders can benefit RV770 due to increased ILP that can be extracted, while the increased resource use of long shaders may mean less threads can be issued on GT200 causing lowered performance. Of course going the other direction would have the opposite effect. Caches and resource availability/management are different, meaning that tradeoffs and choices must be made in when and how data is fetched and used. Fixed function resources are different and optimization of the usage of things like texture filters and the impact of the different setup engines can have a large (and differing with architecture) impact on performance.
We still haven't gotten to the point where we can write simple shader code that just does what we want it to do and expect it to perform perfectly everywhere. Right now it seems like typical usage models favor GT200, while relative performance can vary wildly on RV770 depending on how well the code fits the hardware. G80 (and thus NVIDIA's architecture) did have a lead in the industry for months before R600 hit the scene, and it wasn't until RV670 that AMD had a real competitor in the market place. This could be part of the reason we are seeing fewer titles benefiting from the massive amount of compute available on AMD hardware. But with this launch, AMD has solidified their place in the market (as we will see the 4800 series offers a lot of value), and it will be very interesting to see what happens going forward.
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FITCamaro - Wednesday, June 25, 2008 - link
Yes I noticed it used quite a bit at idle as well. But its load numbers were lower. And as the other guy said, they probably just are still finalizing the drivers for the new cards. I'd expect both performance and idle power consumption to improve in the next month or two.derek85 - Wednesday, June 25, 2008 - link
I think ATI is still fixing/finalizing the Power Play, it should be much lower when new Catalyst comes out.shadowteam - Wednesday, June 25, 2008 - link
If a $200 card can play all your games @ 30+fps, does a $600 card even make sense knowing it'll do no better to your eyes? I see quite a few NV biased elements in your review this time around, and what's all that about the biggest die size TSMC's every produced? GTX's die may be huge, but compared to AMD's, it's only half as efficient. Your review title, I think, was a bit harsh toward AMD. By limiting AMD's victory only up to a price point of $299, you're essentially telling consumers that NV's GTX 2xx series is actually worth the money, which is a terribly biased consumer advice in my opinion. From a $600 GX2 to a $650 GTX 280, Nvidia's actually gone backwards. You know when we talk about AMD's financial struggle, and that the company might go bust in the next few years... part of the reason why that may happen is because media fanatics try to keep things on an even keel, and in doing so they completely forget about what the consumers actually want. No offence to AT, but I've been into media myself, and I can tell when even professionals sound biased.paydirt - Wednesday, June 25, 2008 - link
You're putting words into the reviewer(s) mouth(s) and you know it. I am pretty sure most readers know that bigger isn't better in the computing world; anandtech never said big was good, they are simply pointing out the difference, duh. YOU need to keep in mind that nVidia hasn't done a die shrink yet with the GTX 2XX...I also did not read anything in the review that said it was worth it (or "good") to pay $600 on a GPU, did you? Nope. Thought so. Quit trying to fight the world and life might be different for you.
I'm greatful that both companies make solid cards that are GPGPU-capable and affordable and we have sites like anandtech to break down the numbers for us.
shadowteam - Wednesday, June 25, 2008 - link
Are you speaking on behalf of the reviewers? You've obviously misunderstood the whole point I was trying to make. When you say in your other post that AT is a reviews site and not a product promoter, I feel terribly sorry you because reviews sites are THE best product promoters around, including AT, and Derek pointed this out earlier that AT's too influential to ignore by companies. Well if that is truly the case, why not type in block letters how NV's trying to rip us off, for consumers' sake, may be just for once do it, it'll definitely teach Nvidia a lesson.DaveninCali - Wednesday, June 25, 2008 - link
I completely agree. Anand, the GTX 260/280 are a complete waste of money. You are not providing adequate conclusions. Your data speaks for itself. I know you have to be "friendly" in your conclusions so that you don't arouse the ire of nVidia but the launch of the 260/280 is on the order of the FX series.I mean you can barely test the cards in SLI mode due to the huge power constraints and the price is ABSOLUTELY ridiculous. $1300 for SLI GTX 280. $1300!!!! You can get FOUR 4870 cards for less than this. FOUR OF THEM!!!! You should be screaming how poorly the GTX 280/260 cards are at these performance numbers and price point.
The 4870 beats the GTX 260 in all but one benchmark at $100 less. Not to mention the 4870 consumes less power than the GTX 280. Hell, the 4870 even beats the GTX 280 in some benchmarks. For $350 more, there shouldn't even be ONE game that the 4870 is better at than the GTX 280. Not even more for more than 100% of the price.
I'm not quite sure what you are trying to convey in this article but at least the readers at Anandtech are smart enough to read the graphs for themselves. Given what has been written in the conclusion page (3/4 of it about GPGPU jargon that is totally unnecessary) could you please leave the page blank instead.
I mean come on. Seriously! $1300 compared to $600 with much more performance coming from the 4870 SLI. COME ON!! Now I'm too angry to go to bed. :(
DaveninCali - Wednesday, June 25, 2008 - link
Oh and one other thing. I thought Anandtech was a review site for the consumer. How can you not warn consumers from spending $650 much less $1300 on a piece of hardware that isn't much faster and in some cases not faster at all than another piece of hardware priced at $300/$600 in SLI. It's borderline scam.When you can't show SLI numbers because you can't even find a power supply that can provide the power, at least an ounce of criticism should be noted to try and stop someone from wasting all that money.
Don't you think that consumers should be getting some better advise than this. $1300 for less performance. I feel so sad now. Time to go to sleep.
shadowteam - Wednesday, June 25, 2008 - link
It reminds of that NV scam from yesteryears... I'm forgetting a good part of it, but apparently NV and "some company" racked up some forum/blog gurus to promote their BS, including a guy on AT forums who eventually got rid off due to his extremely biased posts. If AT can do biased reviews, I can pretty much assure you the rest of the reviewers out there are nothing more than just misinformed, over-arrogant media puppets. To those who disagree w/ me or the poster above, let me ask you this... if you were sent out $600 hardware every other week, or in AT's case, every other day (GTX280's from NV board partners), would you rather delightfully, and rightfully, piss NV off, or shut your big mouth to keep the hardware, and cash flowing in?DerekWilson - Wednesday, June 25, 2008 - link
Wow ...I'm completely surprised that you reacted the way you did.
In our GT200 review we were very hard on NVIDIA for providing less performance than a cheaper high end part, and this time around we pointed out the fact that the 4870 actually leads the GTX 260 at 3/4 of the price.
We have no qualms about saying anything warranted about any part no matter who makes it. There's no need to pull punches, as what we really care about are the readers and the technology. NVIDIA really can't bring anything compelling to the table in terms of price / performance or value right now. I think we did a good job of pointing that out.
We have mixed feelings about CrossFire, as it doesn't always scale well and isn't as flexible as SLI -- hopefully this will change with R700 when it hits, but for now there are still limitations. When CrossFire does work, it does really well, and I hope AMD work this out.
NVIDIA absolutely need to readjust the pricing of most of their line up in order to compete. If they don't then AMD's hardware will continue to get our recommendation.
We are here because we love understanding hardware and we love talking about the hardware. Our interest is in reality and the truth of things. Sometimes we can get overly excited about some technology (just like any enthusiast can), but our recommendations always come down to value and what our readers can get from their hardware today.
I know I can speak for Anand when I say this (cause he actually did it before his site grew into what it is today) -- we would be doing this even if we weren't being paid for it. Understanding and teaching about hardware is our passion and we put our heart and soul into it.
there is no amount of money that could buy a review from us. no hardware vendor is off limits.
in the past companies have tried to stop sending us hardware because they didn't like what we said. we just go out and buy it ourselves. but that's not likely to be an issue at this point.
the size and reach of AnandTech today is such that no matter how much we piss off anyone, Intel, AMD, NVIDIA, or any of the OEMs, they can't afford to ignore us and they can't afford to not send us hardware -- they are the ones who want an need us to review their products whether we say great or horrible things about it.
beyond that, i'm 100% sure nvidia is pissed off with this review. it is glowingly in favor of the 4870 and ... like i said ... it really shocks me that anyone would think otherwise.
we don't favor level playing fields or being nice to companies for no reason. we'll recommend the parts that best fit a need at a price if it makes sense. Right now that's 4870 if you want to spend between $300 and $600 (for 2).
While it's really really not worth the money, GTX 280 SLI is the fastest thing out there and some people do want to light their money on fire. Whatever.
i'm sorry you guys feel the way you do. maybe after a good night sleep you'll come back refreshed and see the article in a new light ...
formulav8 - Wednesday, June 25, 2008 - link
Even in the review you claim 4870 is a $400 performer. So why don't you reflect that in the articles title by adding it after the $300 price?? Would be better to do so I think anyways. :)Maybe say 4870 wins up to the $400 price point and likewise with the 4850 version up to the $250 price that you claimed in the article...
This tweak could be helpful to some buyers out there with a specific budget and could help save them some money in the process. :)
Jason