The New PowerTune: Adding Further States

In 2010 AMD introduced their PowerTune technology alongside their Cayman GPU. PowerTune was a new, advanced method of managing GPU voltages and clockspeeds, with the goal of offering better control over power consumption at all times so that AMD could be more aggressive with their clockspeeds. PowerTune’s primary task was to reign in on programs like FurMark – power viruses as AMD calls them – so that these programs would not push a card past its thermal/electrical limits. Consequently, with PowerTune in place AMD would not need to set their maximum GPU clocks as conservatively merely to handle the power virus scenario.

This technology was brought forward for the entire Southern Islands family of GPUs, and remained virtually unchanged. PowerTune as implemented on SI cards without Boost had 3 states – idle, intermediate (low-3D), and high (full-3D). When for whatever reason PowerTune needed to clamp down on power usage to stay within the designated limits, it could either jump states or merely turn down the clockspeed, depending on how far over the limit the card was trying to go. In practice state jumps were rare – it’s a big gap between high and intermediate – so for non-boost cards it would merely turn down the GPU clockspeed until power consumption was where it needed to be.

Modulating clockspeeds in such a manner is a relatively easy thing to implement, but it’s not without its drawbacks. That drawback being that semiconductor power consumption scales at a far greater rate with voltage than it does with clockspeed. So although turning down clockspeeds does reduce power consumption, it doesn’t do so by a large degree. If you want big power savings, you need to turn down the voltage too.

Starting with 7790 and Bonaire, this is exactly what AMD is doing. Gone is pure clockspeed modulation – inferred states in AMD’s nomenclature – and instead AMD is moving to using a larger number of full states. GCN 1.1 has 8 states altogether, with no inferred states between them. With this change, when PowerTune needs to reduce clockspeeds it can drop to a nearby state, reducing power consumption through both clockspeed and voltage reductions at the same time.

With this change state jumping will also be a far more frequent occurrence. The lack of intermediate states and the lack of granularity (8 states over 700MHz is not fine-grained) effectively makes fast state jumping a requirement, as there’s a very good chance dropping down a state will leave some power/performance on the table. So if it’s throttling, 7790 will be able to state jump as quickly as every 10ms (that’s 100 jumps a second), typically bouncing between two or more states in order to keep the card within its limits.

At the same time, AMD’s formula for picking states on non-boost cards has changed. In a move similar to what AMD has done with Richland, AMD’s temperature-agnostic state selection system has been ditched in favor of one that includes temperatures into the calculation, making it a system that is now based on power, temperature, and load. There are some minor benefits to being temperature-agnostic that AMD is giving up – mainly that performance is going to vary a bit with temperature now – but at the end of the day this allows AMD to better min-max their GPUs to hit higher frequencies more often. This also brings them to parity with Intel and NVIDIA, who have long taken temperature into account.

The fact that this is a very boost-like system is not lost on us, and with these changes the line between PowerTune with and without boost starts to become foggy. Both are ultimately going to be doing the same thing – switching states based on power and temperature considerations – the only difference being whether a card adjusts down, or if it adjusts both up and down. In practice we rarely see cards adjust down outside of FurMark, so while PowerTune doesn’t dictate a clockspeed floor, base clocks are still base clocks. In which case the practical difference between whether an AMD card has boost or not is whether it can access some higher voltage, higher clockspeed states that it may not be able to maintain for long periods of time across all workloads. The 7790 isn’t a boost part of course, but AMD’s own presentation neatly lays out where boost would fit in, so if we do see future GCN 1.1 products with boost we have a good idea of what to expect.

Moving on, with the changes to PowerTune will also come changes to AMD’s API for 3rd party utilities, and what information is reported. First and foremost, due to the frequency of state changes with the new PowerTune, AMD will no longer be reporting the instantaneous state. Instead they will be reporting an average of the states used. We don’t know how big the averaging window is – we suspect it’s no more than 2 seconds – but the end result will be that MSI Afterburner, GPU-Z, and other utilities will now see those averages reported as the clockspeed. This will give most users a better idea of what the effective clockspeed (and thereby effective performance) is, but it does mean that it’s going to be virtually impossible to infer the clockspeeds/voltages of AMD’s new states.

The other change is that with the new PowerTune AMD will be exposing new tweaking options to 3rd parties. The current PowerTune (TDP) setting is going to be joined by a separate setting for adjusting a limit called Total Design Current (TDC), which as the name implies is how much current is allowed to be passed into the GPU. AMD limits cards by both TDP and TDC to keep total power, temperatures, and total currents in check, so this will open up the latter to tweakers. Unfortunately utilities with TDC controls were not ready in time for our 7790 review, so we can’t really comment on TDC at this time. With AMD’s changes to PowerTune however (and their insistence on calling TDP thermal management), TDP may be turning into a temperature control while TDC becomes the new power control.

Finally, since these controls are going to be user-accessible, this will spill-over to AMD’s partners. Partners will be able to set their own TDP and TDC limits if they wish, which will help them fine-tune their factory overclocked cards. This will give partners more headroom for such cards as opposed to being stuck shipping cards at AMD’s reference limits, but it means that different cards from different vendors may have different base TDP and TDC limits, along with different clockspeeds. This also means that in the future equalizing clockspeeds may not be enough to equalize two cards.

Bonaire’s Microarchitecture - What We’re Calling GCN 1.1 Meet The Radeon HD 7790 & Sapphire HD 7790 Dual-X Turbo
Comments Locked

107 Comments

View All Comments

  • Death666Angel - Friday, March 22, 2013 - link

    "pulling 7W more than the 7770, a hair more than the 5W difference in AMD’s TBP"
    That 5W is not at the wall though. Factoring in rounding PSU efficiencies, it's very possible that the cards are only drawing 5W more. :)
    "The Sapphire card, despite being overclocked, draws 6W less than our reference 7790."
    Seeing how the Sapphire runs cooler in Furmark, that might explain a Watt or two in reduced power draw, coupled with the efficiency of the PSU, it might explain three or four even. :)
  • pandemonium - Saturday, March 23, 2013 - link

    "NVIDIA has for a long time set the bar on efficiency, but with the 7790 it looks like AMD will finally edge out NVIDIA."

    What is your definition of a long time? As far as efficiency standards, I consider AMD to be better for the end result when looking at the full definition and application of the word. See the spreadsheet I created here about 16 months ago to understand what I mean: http://forums.anandtech.com/showthread.php?t=21507...
  • silverblue - Saturday, March 23, 2013 - link

    You just called Ryan a "dummy", did you, without even checking the statement further down which reads:

    "For anyone looking to pick up a 7790 today, this is being launched ahead of actual product availability (likely to coincide with GDC 2013 next week). Cards will start showing up in the market on April 2nd, which is about a week and a half from now."

    If YOU had read the article, blah blah dumb idiot blah blah. As you've not replied to anybody in particular, your mistargeted rants could be construed as being directed toward the staff themselves, so keep it up and you won't HAVE to worry about what AT is reviewing in future.

    Bottom line - it's faster than the 650 Ti, it's looking to be more efficient than the 650 Ti, and oh look, both have 1GB of GDDR5 on a 128-bit memory interface, which you seem to have forgotten when you leapt down AMD's throat about the 7790, and when you went on your childish tirade about the 5770's 128-bit memory interface earlier.

    As far as I recall, Ryan didn't mention anything about when Titan was available to buy, only that it had launched. Pretty much blows your theory of Ryan hating NVIDIA out of the water, doesn't it?

    I'm not sure if I've said this before, and apologies to everybody else if I have, but I'm done with you, full stop. I can only hope everybody else here decides that not feeding the ignorance you perpetuate on every single AMD article would save them time they could be devoting to something far less boring instead.

    To the staff - is there anything you can do to introduce an Ignore List? Thanks in advance for your response.
  • silverblue - Saturday, March 23, 2013 - link

    A note about threading - doesn't look to be stepping in consistently, so sometimes it's a little difficult to see whom replied to whom.
  • CeriseCogburn - Sunday, March 24, 2013 - link

    You got eveything wrong again, and you failed to read the article not I, and you failed to read my reply addressing half your idiotic non points, so you're the non reader, fool.
    Now I have to correct you multiple times. And you're a waste.
    650TI overclocks and it's only faster in a few amd favor games which are here, of course.
    Strike one for tardboy.
    650Ti runs fine OC'd too, which it does well: " We pushed Gigabyte's GeForce GTX 650 as far as it'd go and achieved a maximum core overclock of 1125 MHz, with the GDDR5 memory operating at 1600. All it took was a 1.15 V GPU voltage. "
    http://www.tomshardware.com/reviews/geforce-gtx-65...
    The 128 bit bus - REPAYMENT for you FOOLS SQUEALING prior, what's so hard to understand ?
    Did you forget all your WHINING ?
    Did you forget your backing up the FAILED theorists with the nVidia dual speed memory ?
    ROFL
    You're up to strike 4 already.
    " Ryan didn't mention anything about when Titan was available to buy, only that it had launched. Pretty much blows your theory of Ryan hating NVIDIA out of the water, doesn't it?"
    NO, so why would it be mentioned if he didn't want anyone to buy it ? Why mention it, that would key in to save for release date, right ?
    Instead we get this gem first off in BOLD to start the article: " Who’s Titan For, Anyhow? "

    Guess that just crushed your idiot backwards bullhockey forever.
    For all you know Ryan mentioned release date anyway.

    You're not "done with me", you get everything WRONG, so you'll be opening your big fat piehole forever, that's how people like you do it. Idiot amd fanboys, all the same.

    Also a beggar child for extra "control", since you "can't be an adult and control yourself" - please give me an ignore button ! I'm a crybaby who can't handle it !
    ROFL
  • philipma1957 - Sunday, March 24, 2013 - link

    One question does your 650Ti pays for itself? this amd will pay for itself via bitcoin. even with the asics. especially if you heat your home with electrical heat.

    nuff said
  • Rajan7667 - Sunday, March 24, 2013 - link

    @form @LinusTech This is new New app for intel lovers. http://www.intel.com/content/www/us/en/gamers/vip-...
  • colonelclaw - Sunday, March 24, 2013 - link

    To Ryan and staff
    As a long-time admirer of AnandTech, I always enjoy reading pretty much every article you post, and have immense respect for all your writers.
    However, I am now utterly fed up with the direction the comment discussions have taken. The general pattern is they start out as debates and end up as pretty nasty personal attacks that have nothing to do with the articles. You may say 'don't read the comments', to which I reply that they used to be an extension of the articles themselves, and were always a source of valuable information.
    It pains me to say this, but if you don't start removing the trolls I will no longer come to this site at all, and I would guess I am not alone in having this opinion.
  • haze4peace - Sunday, March 24, 2013 - link

    I agree 100% and actually sent off a few emails to the staff earlier in the day. I urge others to do so as well so we can put this problem behind us.
  • KnightRAF - Monday, March 25, 2013 - link

    I agree the trolls are out of control and need some pruning back. They have massively lessened my enjoyment of the site the last couple of times I've visited.

Log in

Don't have an account? Sign up now