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.

The Race is Over: 8-channel LPCM, TrueHD & DTS-HD MA Bitstreaming More GDDR5 Technologies: Memory Error Detection & Temperature Compensation
POST A COMMENT

327 Comments

View All Comments

  • mapesdhs - Saturday, September 26, 2009 - link


    > That is quite all right, you fellas make sure to read it all, ...

    But that's the thing S.D., I pretty much don't read any of it. :D (does
    anyone?) First sentence only, then move on.

    Ian.

    Reply
  • SiliconDoc - Monday, September 28, 2009 - link

    Oh, ha ha, another lowlife smart aleck.

    One has to wonder if you do as you say, and only read the first sentence, and move on, why you would care what I've typed, since you cannot imagine anyone does anything different. Heck you shouldn't even notice this, right liar ?

    Yes, another liar, not amazing, not at all.

    No need to modify or delete the sentence prior to this JaredWalton, smarty pants insulter won't read it, but I'm sure you can't resist, for "convenience's" sake of course.

    Oh, I don't have to bring anything up on topic at all, because neither did lowlife skum not reading, he just got his nose awfully browner.
    Reply
  • JarredWalton - Friday, September 25, 2009 - link

    Very happy to have everyone here convinced you don't know what you're talking about? That's the only "truth" you've brought to this party. Marketing generally wants reputable people to promote a product - the "every man" approach. Funny that we don't see crazy people espousing products on TV (well, excepting stuff like Sham Wow!)

    Being crazy like you are in this thread only cements your status as someone who doesn't have a firm grip on reality - someone that can't be trusted. Thanks again for clearing that up so thoroughly.

    I am very happy about it as well! :-D
    Reply
  • erple2 - Tuesday, September 29, 2009 - link

    Yeah, but that "Sham Wow" product works like a freakin' charm...

    http://www.popularmechanics.com/blogs/home_journal...">http://www.popularmechanics.com/blogs/home_journal...
    Reply
  • SiliconDoc - Wednesday, September 30, 2009 - link

    Im' sure you spend your time drooling in front of a TV after you spank your joystick for fps, so know all about wacky commercials you have memorized, and besides, it's a pathetic, all you have left insult, off topic, who cares, pure hatred, no real response, and the 5870 double epic fail IS THE HOTTEST ATI CARD OF ALL TIME! Reply
  • erple2 - Wednesday, September 30, 2009 - link

    What's with the personal attacks? Does that mean that you concede defeat?

    Meh, you've no more credibility. Chill out.
    Reply
  • SiliconDoc - Friday, September 25, 2009 - link

    Yeah, now down to insults, since you lost everything else.

    Let's have your claimed specialty outlined here in context, let's have you come clean on LAPTOP GRAPHICS, and spread the truth about how NVIDIA is so far ahead and has been for quite some time, that it's a JOKE to buy a gaming laptop with ATI graphics on board.
    Come on mmister!
    --
    Now that is REALLY FUNNY ! You grabbed your arrogant unscrupulous self and proclaimed your fairness, but picked a spot where ati is completely EPIC FAIL, and NVIDIA is 1000% the only way to go, PERIOD, and left that MAJOR slap in the face high and dry.
    --
    Great job, yeah, you're the "sane one".
    LOL
    Reply
  • dieselcat18 - Saturday, October 03, 2009 - link

    Nvidia fan-boy, troll, loser....take your gforce cards and go home...we can now all see how terrible ATi is thanks you ...so I really don't understand why people are beating down their doors for the 5800 series, just like people did for the 4800 and 3800 cards. I guess Nvidia fan-boy trolls like you have only one thing left to do and that's complain and cry like the itty-bitty babies that some of you are about the competition that's beating you like a drum.....so you just wait for your 300 series cards to be released (can't wait to see how many of those are available) so you can pay the overpriced premiums that Nvidia will be charging AGAIN !...hahaha...just like all that re-badging BS they pulled with the 9800 and 200 cards...what a joke !.. Oh my, I must say you have me in a mood and the ironic thing is I do like Nvidia as much as ATi, I currently own and use both. I just can't stand fools like you who spout nothing but mindless crap while waving your team flag (my card is better than your's..WhaaWhaaWhaa)...just take yourself along with your worthless opinions and slide back under that slimly rock you came from. Reply
  • JarredWalton - Friday, September 25, 2009 - link

    You've been insulting in this whole thread, so don't go crying to mamma about someone pointing that out. I did go and delete the posts from the person calling you gay and suggesting you should die in various ways, because as bad as you've been you haven't stooped quite that low (yet).

    Laptop issues with ATI... you mean http://www.anandtech.com/mobile/showdoc.aspx?i=356...">like this. Granted, I gave them a chance to address the issues. They failed and my full article on the various Clevo high-end notebooks will make it quite clear how far ahead NVIDIA is in the mobile sector right now.

    "Fair" is treating both sides objectively. ATI has major problems with getting updated graphics drivers out on mobile products, and that's horrible. On the desktop, they don't have such issues for the most part. Yeah, you might have to wait a month or so for a driver update to fix the latest hot release and add CrossFire support... but you have to do the exact same thing for NVIDIA with about the same frequency. Only SLI and CF setups really need the regular driver updates, and in many cases the latest 18x and 19x NVIDIA drivers are slower than 16x and 17x on games that are older than six months.

    Fair is also looking at these results and saying, "gee, I can get a 5870 for $400 (or $360 if you wait a few weeks for supply to bolster up), and that same card has no CrossFire or SLI wonkiness and costs less than the GTX 295 and 4870X2. Okay, 4870X2 and GTX 295 beat it in raw performance in some cases, but I don't think there's a single game where you can say one HD 5870 offers less than acceptable performance at 2560x1600, and I can guarantee there are titles that still have issues with SLI and CrossFire. (Yeah, you need to turn down some details in Crysis to get acceptable performance, but that's true of anything other than the top SLI and CF configs.) I would be more than happy to give up a bit of performance to avoid dealing with the whole multi-GPU ordeal. Why don't you tell us how innovative and awesome tri-SLI and quad-SLI are while you're at it?

    At present, you have contributed more than 20% of the comments to this article, and not a single one has been anything but trolling. Screaming and yelling, insulting others, lying and making stuff up, all in support of a company that is just like any other big company. We don't ban accounts often, but you've more than warranted such action.
    Reply
  • SiliconDoc - Friday, September 25, 2009 - link

    I think it is more than absolutely clear, that in fact, I said my peace, my first post, and was absolutely attacked. I didn't attack, I got attacked, and in fact you have done plenty of attacking as well.
    I have also provided links, to back up my assertions and counter arguments, added the text for easy viewing, and pointed out in very specific detail whay issues with bias I had and why.
    --
    Now you've claimed "all I've done is post FUD".
    It is nothing short of amazing for you to even posit that, however I can certainly understand anyone pointing out the obvious bias problems (in the article no less) is "on thin ice", and after getting attacked, is solely blamed for "no facts".
    ---
    I certainly won't disagree that the 5870 is a good value as appearing if especially if you don't like to deal with 2 cards or 2 cores.
    But my posts never claimed otherwise. I first claimed it was not as good as wanted, was disappointing, and therefore was not the end of what ati had in store.
    Since I have posted on the 5890, which will in fact be 512 bit.
    Now, you don't like losing your points, or someone adept enough, smart enough, and accurate enough to counter them.
    Sorry about that, and sorry that I won't just lay down, as more heaps are shovelled my way.
    You skip my actual points, and go some other tangent.
    1. PhysX is an advantage and best implementation so far.
    your response: "It sucks because only 2 games ar available"
    ---
    Is that correct for you to do ? Is it not the very best so far ? Yes, it is in fact.
    I have remained factual and reasonable, and glad enough to throw back when I'm attacked.
    But the fact remains, I have made absolutely solid 100% poijnts no matter how many times you claim " lying and making stuff up, "
    ---
    Yet of course, what I just said about NVIDIA and laptp chips, you agreed with. So accoring to your own characterization (quite unfair), all you do is scream and lie, too.
    Just wonderful.
    The GT300 is going to blow this 5870 away - the stats themselves show it, and betting otherwise is a bad joke, and if sense is still about, you know it as well.
    Reply

Log in

Don't have an account? Sign up now