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
Lower Idle Power & Better Overcurrent Protection
One aspect AMD was specifically looking to improve in Cypress over RV770 was idle power usage. The load power usage for RV770 was fine at 160W for the HD4870, but that power usage wasn’t dropping by a great deal when idle – it fell by less than half to 90W. Later BIOS revisions managed to knock a few more watts off of this, but it wasn’t a significant change, and even later designs like RV790 still had limits to their idling abilities by only being able to go down to 60W at idle.
As a consequence, AMD went about designing the Cypress with a much, much lower target in mind. Their goal was to get idle power down to 30W, 1/3rd that of RV770. What they got was even better: they came in past that target by 10%, hitting a final idle power of 27W. As a result the Cypress can idle at 30% of the power as RV770, or as compared to Cypress’s load power of 188W, some 14% of its load power.
Accomplishing this kind of dramatic reduction in idle power usage required several changes. Key among them has been the installation of additional power regulating circuitry on the board, and additional die space on Cypress assigned to power regulation. Notably, all of these changes were accomplished without the use of power-gating to shut down unused portions of the chip, something that’s common on CPUs. Instead all of these changes have been achieved through more exhaustive clock-gating (that is, reducing power consumption by reducing clock speeds), something GPUs have been doing for some time now.
The use of clock-gating is quickly evident when we discuss the idle/2D clock speeds of the 5870, which is 150mhz for the core, and 300mhz for the memory . The idle clock speeds here are significantly lower than the 4870 (550/900), which in the case of the core is the source of its power savings as compared to the 4870. As tweakers who have attempted to manually reduce the idle clocks on RV770 based cards for further power savings have noticed, RV770 actually loses stability in most situations if its core clock drops too low. With the Cypress this has been rectified, enabling it to hit these lower core speeds.
Even bigger however are the enhancements to Cypress’s memory controller, which allow it to utilize a number of power-saving tricks with GDDR5 RAM, along with other features that we’ll get to in a bit. With RV770’s memory controller, it was not capable of taking advantage of very many of GDDR5’s advanced features besides the higher bandwidth abilities. Lacking this full bag of tricks, RV770 and its derivatives were unable to reduce the memory clock speed, which is why the 4870 and other products had such high memory clock speeds even at idle. In turn this limited the reduction in power consumption attained by idling GDDR5 modules.
With Cypress AMD has implemented nearly the entire suite of GDDR5’s power saving features, allowing them to reduce the power usage of the memory controller and the GDDR5 modules themselves. As with the improvements to the core clock, key among the improvement in memory power usage is the ability to go to much lower memory clock speeds, using fast GDDR5 link re-training to quickly switch the memory clock speed and voltage without inducing glitches. AMD is also now using GDDR5’s low power strobe mode, which in turn allows the memory controller to save power by turning off the clock data recovery mechanism. When discussing the matter with AMD, they compared these changes to putting the memory modules and memory controller into a GDDR3-like mode, which is a fair description of how GDDR5 behaves when its high-speed features are not enabled.
Finally, AMD was able to find yet more power savings for Crossfire configurations, and as a result the slave card(s) in a Crossfire configuration can use even less power. The value given to us for an idling slave card is 20W, which is a product of the fact that the slave cards go completely unused when the system is idling. In this state slave cards are still capable of instantaneously ramping up for full-load use, although conceivably AMD could go even lower still by powering down the slave cards entirely at a cost of this ability.
On the opposite side of the ability to achieve such low idle power usage is the need to manage load power usage, which was also overhauled for the Cypress. As a reminder, TDP is not an absolute maximum, rather it’s a maximum based on what’s believed to be the highest reasonable load the card will ever experience. As a result it’s possible in extreme circumstances for the card to need power beyond what its TDP is rated for, which is a problem.
That problem reared its head a lot for the RV770 in particular, with the rise in popularity of stress testing programs like FurMark and OCCT. Although stress testers on the CPU side are nothing new, FurMark and OCCT heralded a new generation of GPU stress testers that were extremely effective in generating a maximum load. Unfortunately for RV770, the maximum possible load and the TDP are pretty far apart, which becomes a problem since the VRMs used in a card only need to be spec’d to meet the TDP of a card plus some safety room. They don’t need to be able to meet whatever the true maximum load of a card can be, as it should never happen.
Why is this? AMD believes that the instruction streams generated by OCCT and FurMark are entirely unrealistic. They try to hit everything at once, and this is something that they don’t believe a game or even a GPGPU application would ever do. For this reason these programs are held in low regard by AMD, and in our discussions with them they referred to them as “power viruses”, a term that’s normally associated with malware. We don’t agree with the terminology, but in our testing we can’t disagree with AMD about the realism of their load – we can’t find anything that generates the same kind of loads as OCCT and FurMark.
Regardless of what AMD wants to call these stress testers, there was a real problem when they were run on RV770. The overcurrent situation they created was too much for the VRMs on many cards, and as a failsafe these cards would shut down to protect the VRMs. At a user level shutting down like this isn’t a very helpful failsafe mode. At a hardware level shutting down like this isn’t enough to protect the VRMs in all situations. Ultimately these programs were capable of permanently damaging RV770 cards, and AMD needed to do something about it. For RV770 they could use the drivers to throttle these programs; until Catalyst 9.8 they detected the program by name, and since 9.8 they detect the ratio of texture to ALU instructions (Ed: We’re told NVIDIA throttles similarly, but we don’t have a good control for testing this statement). This keeps RV770 safe, but it wasn’t good enough. It’s a hardware problem, the solution needs to be in hardware, particularly if anyone really did write a power virus in the future that the drivers couldn’t stop, in an attempt to break cards on a wide scale.
This brings us to Cypress. For Cypress, AMD has implemented a hardware solution to the VRM problem, by dedicating a very small portion of Cypress’s die to a monitoring chip. In this case the job of the monitor is to continually monitor the VRMs for dangerous conditions. Should the VRMs end up in a critical state, the monitor will immediately throttle back the card by one PowerPlay level. The card will continue operating at this level until the VRMs are back to safe levels, at which point the monitor will allow the card to go back to the requested performance level. In the case of a stressful program, this can continue to go back and forth as the VRMs permit.
By implementing this at the hardware level, Cypress cards are fully protected against all possible overcurrent situations, so that it’s not possible for any program (OCCT, FurMark, or otherwise) to damage the hardware by generating too high of a load. This also means that the protections at the driver level are not needed, and we’ve confirmed with AMD that the 5870 is allowed to run to the point where it maxes out or where overcurrent protection kicks in.
On that note, because card manufacturers can use different VRMs, it’s very likely that we’re going to see some separation in performance on FurMark and OCCT based on the quality of the VRMs. The cheapest cards with the cheapest VRMs will need to throttle the most, while luxury cards with better VRMs would need to throttle little, if at all. This should make little difference in stock performance on real games and applications (since as we covered earlier, we can’t find anything that pushes a card to excess) but it will likely make itself apparent in overclocking. Overclocked cards - particularly those with voltage modifications – may hit throttle situations in normal applications, which means the VRMs will make a difference here. It also means that overclockers need to keep an eye on clock speeds, as the card shutting down is no longer a tell-tale sign that you’re pushing it too hard.
Finally, while we’re discussing the monitoring chip, we may as well talk about the rest of its features. Along with monitoring the GPU, it also is a PWM controller. This means that the PWM controller is no longer a separate part that card builders add themselves, and as such we won’t be seeing any cards using a 2pin fixed speed fan to save money on the PWM controller. All Cypress cards (and presumably, all derivatives) will have the ability to use a 4pin fan built-in.
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SiliconDoc - Wednesday, September 30, 2009 - link
I was here before this site was even on the map let alone on your radar, and have NEVER had any other acct name.I will wait for your APOLOGY.
ol1bit - Friday, September 25, 2009 - link
Goodbye 8800gt SLI... nothing has given me the bang for the buck upgrade that this card does!I paid $490 for my SLI 8800Gt's in 11/07
$379 Sweetness!
Brazos - Thursday, September 24, 2009 - link
I always get nostalgic for Tech TV when a new gen of video cards come out. Watching Leo, Patrick, et al. discuss the latest greatest was like watching kids on Christmas morning. And of course there was Morgan.totenkopf - Thursday, September 24, 2009 - link
SiliconDoc, this is pathetic. Why are you so upset? No one cares about arguing the semantics of hard or paper launches. Besides, where the F is Nvidias Gt300 thingy? You post here more than amd fanboys, yet you hate amd... just hibernate until the gt300 lauunches and then you can come back and spew hatred again.Seriously... the fact that you cant even formulate a cogent argument based on anything performance related tells me that you have already ceded the performance crown to amd. Instead, you've latched onto this red herring, the paper launch crap. stop it. just stop it. You're like a crying child. Please just be thankful that amd is noww allowing you to obtain more of your nvidia panacea for even less money!
Hooray competition! EVERYONE WINS! ...Except silicon doc. He would rather pay $650 for a 280 than see ati sell one card. Ati is the best thing that ever happened to nvidia (and vice versa) Grow the F up and dont talk about bias unless you have none yourself. Hope you dont electrocute yourself tonight while making love to you nvidia card.
SiliconDoc - Thursday, September 24, 2009 - link
" Hooray competition! EVERYONE WINS! ...Except silicon doc. He would rather pay $650 for a 280 than see ati sell one card."And thus you have revealed your deep seated hatred of nvidia, in the common parlance seen.
Frankly my friend, I still have archived web pages with $500 HD2900XT cards from not that long back, that would easily be $700 now with the inflation we've seen.
So really, wnat is your red raving rooster point other than you totally excuse ATI tnat does exactly the same thing, and make your raging hate nvidia whine, as if "they are standalone guilty".
You're ANOTHER ONE, that repeats the same old red fan cleche's, and WON'T OWN UP TO ATI'S EXACT SAME BEHAVIOR ! Will you ? I WANT TO SEE IT IN TEXT !
In other words, your whole complaint is INVALID, because you apply it exclusively, in a BIASED fashion.
Now tell me about the hundres of dollars overpriced ati cards, won't you ? No, you won't. See that is the problem.
silverblue - Friday, September 25, 2009 - link
If you think companies are going to survive without copying what other companies do, you're sadly mistaken.Yes, nVidia has made advances, but so has ATI. When nVidia brought out the GF4 Ti series, it supported Pixel Shader 1.3 whereas ATI's R200-powered 8500 came out earlier with the more advanced Pixel Shader 1.4. ATI were the first of the two companies to introduce a 256-bit memory bus on their graphics cards (following Matrox). nVidia developed Quincunx, which I still hold in high regard. nVidia were the first to bring out Shader Model 3. I still don't know of any commercially available nVidia cards with GDDR5.
We could go on comparing the two but it's essential that you realise that both companies have developed technologies that have been adopted by the other. However, we wouldn't be so far down this path without an element of copying.
The 2900XT may be overpriced because it has GDDR4. I'm not interested in it and most people won't be.
"In other words, your whole complaint is INVALID, because you apply it exclusively, in a BIASED fashion. " Funny, I thought we were seeing that an nauseum from you?
Why did I buy my 4830? Because it was cheaper than the 9800GT and performed at about the same level. Not because I'm a "red rooster".
ATI may have priced the 5870 a little high, but in terms of its pure performance, it doesn't come too far off the 295 - a card we know to have two GPUs and costs more. In the end, perhaps AMD crippled it with the 256-bit interface, but until they implement one you'll be convinced that it's a limitation. Maybe, maybe not. GT300 may just prove AMD wrong.
SiliconDoc - Wednesday, September 30, 2009 - link
You have absolutely zero proof that we wouldn't be further down this path without the "competition".Without a second company or third of fourth or tenth, the monopoly implements DIVISIONS that complete internally, and without other companies, all the intellectual creativity winds up with the same name on their paycheck.
You cannot prove what you say has merit, even if you show me a stagnant monopoly, and good luck doing that.
As ATI stagnated for YEARS, Nvidia moved AHEAD. Nvidia is still ahead.
In fact, it appears they have always been ahead, much like INTEL.
You can compare all you want but "it seems ati is the only one interested in new technology..." won't be something you'll be blabbing out again soon.
Now you try to pass a lesson, and JARED the censor deletes responses, because you two tools think you have a point this time, but only with your deleting and lying assumptions.
NEXT TIME DON'T WAIL ATI IS THE ONLY ONE THAT SEEMS INTERESTED IN IMPLEMENTING NEW TECHGNOLOGY.
DON'T SAY IT THEN BACKTRACK 10,000 % WHILE TRYING TO "TEACH ME A LESSON".
You're the one whose big far red piehole spewed out the lie to begin with.
Finally - Friday, September 25, 2009 - link
The term "Nvidiot" somehow sprung to my mind. How come?silverblue - Thursday, September 24, 2009 - link
Youre spot on about his bias. Every single post consists of trash-talking pretty much every ATI card and bigging up the comparative nVidia offering. I think the only product he's not complained about is the 4770, though oddly enough that suffered horrific shortage issues due to (surprise) TSMC.Even if there were 58x0 cards everywhere, he'd moan about the temperature or the fact it should have a wider bus or that AMD are finally interested in physics acceleration in a proper sense. I'll concede the last point but in my opinion, what we have here is a very good piece of technology that will (like CPUs) only get better in various aspects due to improving manufacturing processes. It beats every other single GPU card with little effort and, when idle, consumes very little juice. The technology is far beyond what RV770 offers and at least, unlike nVidia, ATI seems more interested in driving standards forward. If not for ATI, who's to say we'd have progressed anywhere near this far?
No company is perfect. No product is perfect. However, to completely slander a company or division just because he buys a competitor's products is misguided to say the least. Just because I own a PC with an AMD CPU, doesn't mean I'm going to berate Intel to high heaven, even if their anti-competitive practices have legitimised such criticism. nVidia makes very good products, and so does ATI. They each have their own strengths and weaknesses, and I'd certainly not be using my 4830 without the continued competition between the two big performance GPU manufacturers; likewise, SiliconDoc's beloved nVidia-powered rig would be a fair bit weaker (without competition, would it even have PhysX? I doubt it).
SiliconDoc - Thursday, September 24, 2009 - link
Well, that was just amazing, and you;re wrong about me not complaining about the 4770 paper launch, you missed it.I didn't moan about the temperature, I moaned about the deceptive lies in the review concerning temperatures, that gave ATI a complete pass, and failed to GIVE THE CREDIT DUE THAT NVIDIA DESERVES because of the FACTS, nothing else.
The article SPUN the facts into a lying cobweb of BS. Juzt like so many red fans do in the posts, and all over the net, and you've done here. It is so hard to MAN UP and admit the ATI cards run hotter ? Is is that bad for you, that you cannot do it ? Certainly the article FAILED to do so, and spun away instead.
Next, you have this gem " at least, unlike nVidia, ATI seems more interested in driving standards forward."
ROFLMAO - THIS IS WHAT I'M TALKING ABOUT.
Here, let me help you, another "banned" secret that the red roosters keep to their chest so their minions can spew crap like you just did: ATI STOLE THE NVIDIA BRIDGE TECHNOLOGY, ATI HAD ONLY A DONGLE OUTSIDE THE CASE, WHILE NVIDIA PROGRESSED TO INTERNAL BRIDGE. AFTER ATI SAW HOW STUPID IT WAS, IT COPIED NVIDIA.
See, now there's one I'll bet a thousand bucks you never had a clue about.
I for one, would NEVER CLAIM that either company had the lock on "forwarding technbology", and I IN FACT HAVE NEVER DONE SO, EVER !
But you red fans spew it all the time. You spew your fanboyisms, in fact you just did, that are absolutely outrageous and outright red leaning lies, period!
you: " at least, unlike nVidia, ATI seems more interested in driving standards forward...."
I would like to ask you, how do you explain the never before done MIMD core Nvidia has, and will soon release ? How can you possibly say what you just said ?
If you'd like to give credit to ATI going with DRR4 and DDR5 first, I would have no problem, but you people DON'T DO THAT. You take it MUCH FURTHER, and claim, as you just did, ATI moves forward and nvidia does not. It's a CONSTANT REFRAIN from you people.
Did you read the article and actually absorb the OpenCL information ? Did you see Nvidia has an implementation, is "ahead" of ati ? Did you even dare notice that ? If not, how the hell not, other than the biased wording the article has, that speaks to your emotionally charged hate Nvidia mindset :
"However, to completely slander a company or division just because he buys a competitor's products is misguided to say the least."
That is NOT TRUE for me, as you stated it, but IT IS TRUE FOR YOU, isn't it ?
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You in fact SLANDERED Nvidia, by claiming only ATI drives forward tech, or so it seems to you...
I've merely been pointing out the many statements all about like you just made, and their inherent falsehood!
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Here next, you pull the ol' switcharoo, and do what you say you won't do, by pointing out you won't do it! roflmao: " doesn't mean I'm going to berate Intel to high heaven, even if their anti-competitive practices have legitimised such criticism.."
Well, you just did berate them, and just claimed it was justified, cinching home the trashing quickly after you claimed you wouldn't, but have utterly failed to point out a single instance, unlike myself- I INCLUDE the issues and instances, pointing them out imtimately and often in detail, like now.
LOL you: " I'd certainly not be using my 4830 without ...."
Well, that shows where you are coming from, but you're still WRONG. If either company dies, the other can move on, and there's very little chance that the company will remain stagnant, since then they won't sell anything, and will die, too.
The real truth about ATI, which I HAVE pointed out before, is IT FELL OFF THE MAP A FEW YEARS BACK AND ALTHOUGH PRIOR TO THAT TIME WAS COMPETITIVE AND PERHAPS THE VERY BEST, IT CAVED IN...
After it had it's "dark period" of failure and depair, where Nvidia had the lone top spot, and even produced the still useful and amazing GTX8800 ultimate (with no competition of any note in sight, you failed to notice, even to this day - and claim the EXACT OPPOSITE- because you, a dead brained red, bought the "rebrand whine" lock stock and barrel), ATI "re-emerged", and in fact, doesn't rteally deserve praise for falling off the wagon for a year or two.
See, that's the truth. The big fat red fib, you liars can stop lying about is the "stagnant technology without competition" whine.
ATI had all the competition it could ever ask for, and it EPIC FAILED for how many years ? A couple, let's say, or one if you just can't stand the truth, and NVIDIA, not stagnated whatsoever, FLEW AHEAD AND RELEASED THE MASSIVE GTX8800 ULTIMATE.
So really friend, just stop the lying. That's all I ask. Quit repeating the trashy and easily disproved ati cleche's.
Ok ?