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
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  • Zool - Friday, September 25, 2009 - link

    "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."
    If not than it would be a sad day for nvidia after more than 2 years of nothing.
    But the 5870 can still blow away any other card around. With DX11 fixed tesselators in pipeline and compute shader postprocessing (which will finaly tax the 1600 stream procesors)it will look much better than curent dx9. The main advantage of this card is the dx11 which of course nvidia doesnt hawe. And maybe the dewelopers will finaly optimize for the ati vector architecture if there isnt any other way meant to be played(payed) :).
    Actualy nvidia couldnt shrink the last gen to 40nm with its odd high frequency scalar shaders (which means much more leakage) so i wouldent expect much more from nvidia than double the stats and make dx11 either.
    Reply
  • SiliconDoc - Friday, September 25, 2009 - link

    Here more new NVidia cards, so the fasle 2 years complaint is fixzling fast.
    Why this hasn't been mentioned here at anadtech yet I'm not sure, but of course...

    http://www.fudzilla.com/content/view/15698/1/">http://www.fudzilla.com/content/view/15698/1/

    Gigabyte jumps the gun with 40nm

    According to our info, Nvidia's GT 220, 40nm GT216-300 GPU, will be officially announced in about three weeks time.

    The Gigabyte GT 220 works at 720MHz for the core and comes with 1GB of GDDR3 memory clocked at 1600MHz and paired up with a 128-bit memory interface. It has 48 stream processors with a shader clock set at 1568MHz.
    --
    See, there's a picture as well. So, it's not like nothing has been going on. It's also not "a panicky response to regain attention" - it is the natural progression of movement to newer cores and smaller nm processes, and those things take time, but NOT the two years plus ideas that spread around....
    Reply
  • SiliconDoc - Friday, September 25, 2009 - link

    The GT200 was released on June 16th and June17th, 2008, definitely not more than 2 years ago, but less.
    The 285 (nm die shrink) on January 15th, 2009, less than 1 year ago.

    The 250 on March 3rd this year, though I wouldn't argue you not wanting to count that.

    I really don't think I should have to state that you are so far off the mark, it is you, not I, that might heal with correction.

    Next, others here, the article itself, and the ati fans themselves won't even claim the 5870 blows away every other card, so that statement you made is wrong, as well.
    You could say every other single core card - no problem.
    Let's hope the game scenes do look much better, that would be wonderful, and a fine selling point for W7 and DX11 (and this casrd if it is, or remains, the sole producer of your claim).
    I suggest you check around, the DX11 patch for Battleforge is out, so maybe you can find confirmation of your "better looking" games.

    " Actualy nvidia couldnt shrink the last gen to 40nm with its odd high frequency scalar shaders "
    I believe that is also wrong, as they are doing so for mobile.
    What is true is ATI was the ginea pig for 40nm, and you see, their yeilds are poor, while NVidia, breaking in later, has had good yeilds on the GT300, as stated by - Nvidia directly, after ATI made up and spread lies about 9 or less per wafer. (that link is here, I already posted it)
    ---
    If Nvidia's card doubles performance of the 285, twice the frames at the same reso and settings, I will be surprised, but the talk is, that or more. The stats leaked make that a possibility. The new MIMD may be something else, I read 6x-15x the old performance in certain core areas.
    What Nvidia is getting ready to release is actually EXCITING, is easily described as revolutionary for videocards, so yes, a flop would be a very sad day for all of us. I find it highly unlikely, near impossible, the silicon is already being produced.
    The only question yet is how much better.
    Reply
  • Zool - Friday, September 25, 2009 - link

    I want to note also that the 5870 is hard to find which means the 40nm tsmc is still far from the last gen 55nm. After they manage it to get on the 4800 level the prices will be different. And maybe the gt300 is still far away. Reply
  • mapesdhs - Friday, September 25, 2009 - link


    Is there any posting moderation here? Some of the flame/troll posts
    are getting ridiculous. The same thing is happening on toms these days.

    Jarred, best not to reply IMO. I don't think you're ever going to get
    a logical response. Such posts are not made with the intent of having
    a rational discussion. Remember, as Bradbury once said, it's a sad
    fact of nature that half the population have got to be below average. :D

    Ian.


    Reply
  • Zool - Friday, September 25, 2009 - link

    I would like to see some more tests on power load. Actualy i dont think there are too many people with 2560*1600 displays. There are still plenty people with much lower resolutions like 1680*1050 and play with max imagequality. With VSync on if u reduce 200fps to 60fps u get much less gpu temps and also power load.(things like furmark are miles away from real world) On LCD there is no need to turn it off just if u benchmark and want more fps. I would like to see more power load tests with diferent resolutions and Vsync on.(And of course not with crysis)
    Also some antialiasing tests, the adaptive antialiasing on 5800 is now much faster i read.And the FSAA is of course blurry, it was always so. If u render the image in 5120*3200 on your 2560*1600 display and than it combines the quad pixels it will seems like its litle washed out. Also in those resolution even the highress textures will begin to pixalate even in closeup so the combined quad pixels wont resemble the original. Without higher details in game the FSAA in high resolution will just smooth the image even more. Actualy it always worked this way even on my gf4800.

    Reply
  • SiliconDoc - Friday, September 25, 2009 - link

    PS - a good friend of mine has an ATI HD2900 pro with 320 shaders (a strange one not generally listed anywhere) that he bought around the time I was showing him around the egg cards and I bought an ATI card as well.
    Well, he's a flight simmer, and it has done quite well for him for a about a year, although in his former Dell board it was LOCKED at 500mhz 503mem 2d and 3d, no matter what utility was tried, and the only driver that worked was the CD that came with it.
    Next on a 570 sli board he got a bit of relief, an with 35 various installs or so, he could sometimes get 3d clocks to work.
    Even with all that, it performed quite admirably for the strange FS9 not being an NVidia card.
    Just the other day, on his new P45 triple pci-e slot, after 1-2 months running, another friend suggested he give OCCT a go, and he asked what is good for stability (since he made 1600fsb and an impressive E4500 (conroe) 200x11/2200 stock to a 400x8/ 3200mhz processor overclock for the past week or two). "Ten minutes is ok an hour is great" was the response.
    Well, that HD2900pro and OCCT didn't like eachother much either - and DOWN went the system, 30 seconds in, cooking that power supply !
    --- LOL ---
    Now that just goes to show you that hiding this problem with the 4870 and 4890 for so many months, not a peep here... is just not good for end users...
    ---
    Thanks a lot tight lipped "nothing is wrong with ATI cards" red fans. Just wonderful.
    ---
    He had another PS and everything else is OK

    , and to be quite honest and frank and fair as I near always am, that HD2900pro still does pretty darn good for his flight simming ( and a few FPS we all play sometimes) and he has upgraded EVERYTHING else already at least once, so on that card, well done for ATI. (well depsite the drivcer issues, 3d mhz issues, etc)
    Oh, and he also has a VERY NICE 'oc on it now(P45 board) - from 600/800 core/mem 3D to 800/1000, and 2d is 500/503, so that's quite impressive.
    Reply
  • SiliconDoc - Wednesday, September 30, 2009 - link

    Ahh, isn't that typical, the 3 or 4 commenters raving for ati "go dead silent" on this furmark and OCCT issue.
    --
    "It's ok we never mentioned it for a year plus as we guarded our red fan inner child."
    (Ed. note: We "heard" nvidia has a similar implementation")
    WHATEVER THAT MEANS !
    ---
    I just saw (somewhere else) another red fanatic bloviating about his 5870 only getting up to 76C in Furmark. ROFLMAO
    --
    Aww, the poor schmuck didn't know the VRM's were getting cut back and it was getting throttled from the new "don't have a heat explosion" tiny wattage crammed hot running ati core.
    Reply
  • SiliconDoc - Friday, September 25, 2009 - link

    Well you brought to mind another sore spot for me.
    In the article, when the 4870 and 4890 FAIL furmark and OCCT, we are suddenly told, after this many MONTHS, that a blocking implementation in ati driver version 9.2 was put forth by ATI, so their cards wouldn't blow to bits on furmark and OCCT.
    I for one find that ABSOLUTELY AMAZING that this important information took this long to actually surface at red central - or rather, I find it all too expected, given the glaring bias, ever present.
    Now, the REASON this information finally came forth, other thanb the epic fail, is BECAUSE the 5870 has a "new technology" and no red fan site can possibly pass up bragging about something new in a red core.
    So the brag goes on, how protection bits in the 5870 core THROTTLE BACK the VRM's when heat issues arise, hence allowing for cheap VRM's & or heat dissipation issues to divert disaster.
    That's wonderful, we finally find out about ANOTHER 4870 4980 HEAT ISSUE, and driver hack by ATI, and a failure to RUN THE COMMON BENCHMARKS we have all used, this late in the game.
    I do have to say, the closed mouthed rabid foam contained red fans are to appluaded for their collective silence over this course of time.
    Now, further bias revealed in tha article - the EDITOR makes sure to chime in, and notes ~"we have heard Nvidia has a similar thing".
    What exactly that similar thing is, and whom the Editor supposedly heard it from, is never made clear.
    Nonetheless, it is a hearty excuse and edit for, and in favor of, EXCUSING ATI's FAILURES.

    Nonetheless, ALL the nvidia cards passed all the tests, and were 75% in number to the good cooler than the ATI's that were- ATI all at 88C-90C, but, of course, the review said blandly in a whitewash, blaming BOTH competitors nvidia and ati - "temps were all over the place" (on load).
    (The winning card GTX295 @ 90C, and 8800GT noted 92C *at MUCH reduced case heat and power consumption, hence INVALID as comparison)
    Although certain to mention the GT8800 at 92C, no mention of the 66C GTX250 or GTX260 winners, just the GTX275 @ 75C, since that was less of a MAJOR EMBARRASSMENT for the ATI heat load monsters !
    Now THERE'S A REAL MONSTER - AND THAT'S ALL OF THE ATI CARDS TESTED IN THIS REVIEW ! Not just the winning nvidia, while the others that matter (can beat 5870 in sli or otherwise) hung 24C to 14C lower under load.
    So, after all that, we have ANOTHER BIAS, GLARING BIAS - the review states " there are no games we know of, nor any we could find, that cause this 5870 heat VRM throttling to occur".
    In other words, we are to believe, it was done in the core, just for Furmark and OCCT, or, that it was done as precaution and would NEVER come into play, yes, rest assured, it just won't HAPPEN in the midst of a heavy firefight when your trigger finger is going 1,000mph...
    So, I found that just CLASSIC for this place. Here is another massive heat issue, revealed for the first time for 4870 and 4890 months and months and months late, then the 5870 is given THE GOLDEN EXCUSE and massive pass, as that heat reducing VRM cooling voltage cutting framerate lowering safety feature "just won't kick in on any games".
    ROFL
    I just can't help it, it's just so dang typical.
    Reply
  • DigitalFreak - Friday, September 25, 2009 - link

    Looks like SnakeOil has yet ANOTHER account. Reply

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