• What
    is this?
    You've landed on the AMD Portal on AnandTech. This section is sponsored by AMD. It features a collection of all of our independent AMD content, as well as Tweets & News from AMD directly. AMD will also be running a couple of huge giveaways here so check back for those.
    PRESENTED BY

August is not typically a busy time of the year for the GPU industry. But this is quickly turning out to be anything but a normal August. Between professional and consumer graphics cards we have a busy week ahead.

Kicking things off on the consumer side today, AMD is announcing that they will be releasing a new Radeon HD 7950 with higher clockspeeds. The new 7950, to be called the Radeon HD 7950, is a revised version of the existing 7950 that is receiving the same performance enhancements that the 7970 received back in June, which were the basis of the Radeon HD 7970 GHz Edition.

AMD GPU Specification Comparison
  AMD Radeon HD 7970 GHz Edition AMD Radeon HD 7970 AMD Radeon HD 7950 (w/Boost) AMD Radeon HD 7950
Stream Processors 2048 2048 1792 1792
Texture Units 128 128 112 112
ROPs 32 32 32 32
Core Clock 1000MHz 925MHz 850MHz 800MHz
Boost Clock 1050MHz N/A 925MHz N/A
Memory Clock 6GHz GDDR5 5.5GHz GDDR5 5GHz GDDR5 5GHz GDDR5
Memory Bus Width 384-bit 384-bit 384-bit 384-bit
VRAM 3GB 3GB 3GB 3GB
FP64 1/4 1/4 1/4 1/4
Transistor Count 4.31B 4.31B 4.31B 4.31B
PowerTune Limit 250W+ 250W 225W 200W
Manufacturing Process TSMC 28nm TSMC 28nm TSMC 28nm TSMC 28nm
Architecture GCN GCN GCN GCN
Launch Date 06/22/2012 01/09/2012 08/17/2012 01/31/2012
Launch Price $499 $549 $329 $449

Diving right into things, the new 7950 – which we’re going to call the 7950B for lack of a distinct official name – is a performance enhanced part based on the same process that AMD used to create the Radeon HD 7970 GHz Edition. Like the 7970GE, AMD is doing two things here for the 7950B: they’re increasing the base clockspeed, and they’re also introducing their GPU turbo boost functionality to potentially push clockspeeds higher.

With these enhancements the clockspeeds for the 7950B will be 850MHz for the base clock, 925MHz for the boost clock, and the memory clock is kept at 5GHz. As a result the GPU clockspeed difference is anywhere between 50MHz (6%) at its base and 125MHz (16%) at the highest boost clock. Because only the core clock is changing, the performance difference between the 7950 and 7950B will be heavily dependent on whether the game/application at hand is GPU limited; heavily GPU limited tasks (that can stay within the power limits) will benefit the most, while memory bandwidth limited or CPU limited tasks may not benefit at all.

So how is AMD pulling this off? We’ve already covered AMD’s PowerTune Technology With Boost (PT Boost) in depth with the 7970GE review, but in case you missed it, here’s a quick refresher. At its most basic level, PT is a combination of BIOS and Catalyst driver changes that allow AMD to overdrive the GPU when conditions permit. In practice PT Boost is very similar to NVIDIA’s GPU Boost. Both technologies are based around the concept of a base clock (or engine clock in AMD’s terminology) with a set voltage, and then one or more boost bins with an associated voltage that the GPU can move to as power/thermal conditions permit. In essence PT Boost allows suitably equipped cards to overvolt and overclock themselves to a limited degree.

Under the hood, the current incarnation of PT Boost is primarily designed to take advantage of AMD’s previously conservative specifications for the Radeon HD 7950. In implementing their PowerTune technology, AMD opted to base their power consumption calculations around the worst case scenario for leakage, thereby ensuring no card ever exceeded its designated PowerTune limit at an opportunity cost of having not maximized performance. PT Boost effectively inverses this methodology, implementing a Digital Temperate Estimation (DTE) algorithm to determine the real leakage at any given time. By accurately estimating a GPU’s leakage AMD can push the GPU closer to its limits, thereby maximizing its performance. The tradeoff of course is that real power consumption will increase, as AMD’s cards are now eating into what was previously a large power buffer.

Moving on, since PT Boost was designed against AMD’s existing hardware, AMD and their partners have been taking advantage of this design choice by deploying it on existing 7900 series hardware. Just as how the 7970GE was built on existing 7970 board designs, the 7950B specs are intended to be deployed as an upgrade for existing 7950 designs. As with the 7970GE, the real change here is that AMD is qualifying their GPUs to operate at higher voltage/clockspeed combinations. For our converted reference card the new base voltage is 1.125v for 850MHz, up from 1.093v for 800MHz on the original 7950. Meanwhile the boost voltage goes much higher, with AMD using a rather high 1.25v for the 925MHz boost clock. In fact this ends up being the highest voltage a reference Tahiti card operates at, as even the reference 7970GE only used 1.218v.

Radeon HD 7950 Series Voltages
Ref 7970B Base Voltage Ref 7950B Boost Voltage Ref 7950 Base Voltage
1.125v 1.25v 1.093v

These numbers paint an interesting picture, albeit not one that is particularly rosy. For the 7970 AMD was already working with top bin Tahiti GPUs, so to make a 7970GE they just needed to apply a bit more voltage and call it a day. The 7950 on the other hand is largely composed of salvaged GPUs that failed to meet 7970 specifications. GPUs that failed due to damaged units aren’t such a big problem here, but GPUs that failed to meet clockspeed targets are another matter. As a result of the fact that AMD is working with salvaged GPUs, AMD has to apply a lot more voltage to a 7950 to guarantee that those poorly clocking GPUs will correctly hit the 925MHz boost clock.

With that in mind however, all of this appears to be a calculated risk on AMD’s part. The reality of AMD’s situation is that Tahiti can’t compete with GK104’s power efficiency. Tahiti is a clearly superior GPU for compute purposes, but when it comes to gaming AMD and NVIDIA’s best products are virtually tied in performance, a matchup that leaves NVIDIA holding the smaller, lower power GPU. So what is AMD to do in such a situation? If the 7970GE didn’t make it obvious, the 7950B does: forgo all pretense of power efficiency and focus on performance-per-dollar.

With both the 7970GE and 7950B AMD has notably increased their power consumption. We’ll take a look at the numbers in-depth in a bit, but the important change is that based on our data the 7950B is now drawing more power than the GTX 680. This isn’t necessarily a bad tradeoff – after all everyone likes more performance – but like all tradeoffs it does come with consequences. For the 7950B in particular, this means that the TDP has gone up from 200W for the 7950 to 225W for the 7950B.

Launch Details
POST A COMMENT

58 Comments

View All Comments

  • Rick83 - Tuesday, August 14, 2012 - link

    And I thought that we were over that chapter with the last generation of cards.
    Oh well, let;s turn up that voltage and crank up those clocks, we can always get triple 8-pin pcie power!

    225 Watts in an upper mid range card is just a bit too much.
    Reply
  • bennyg - Wednesday, August 15, 2012 - link

    </IMO>

    If the card can do it, why not improve the primary functionality of this class of GPU, crunching graphics. If for some reason 200W is OK for you and 225W isn't... cue tada.wav now - don't upgrade it's BIOS.

    I've heard too the new model Viper gets no more MPG than the Gen 4.
    Reply
  • JPForums - Wednesday, August 15, 2012 - link

    225 Watts in an upper mid range card is just a bit too much.


    The 7950 isn't upper mid range. (At least in AMD's eyes.)
    High end - 79xx
    Upper Mid range - 78xx
    Lower Mid range - 77xx
    Low End - Higher end A-Series processors (76xx/75xx)
    Entry Level - Lower end A-Series/E series Processors

    I understand the confusion given the low end discrete market has been largely displaced by Integrated GPU's. I also have a hard time deciding whether the 7870 performs like a high end card, or the 7950 performs like an upper mid range card. I like to draw the line at the up coming GTX660(Ti). I wouldn't call my GTX670 mid range, but I wouldn't call any form of GTX660 high end. My guess is that the 7950B will slot in between the two in performance. If it doesn't then it will go down as a high end card that performs like an upper mid range card.
    I'm glad they revamped the 7950 as it had plenty of power headroom for a high end card and its performance was too close to the 7870. I just wish they would have named the new 7950/7970 - 7955/7975 (or if you prefer 7960/7980). They could still let the 7950 fade out. There is still no need for a new reference design. There would be no confusion when buying in the interim. It would accurately reflect the marginal upgrade in performance. Honestly with all the new model numbers assigned to old parts that both nVidia and AMD use to make products appear new and better, I can't imagine why either of them would choose not to rename a legitimately different part.
    Reply
  • JPForums - Saturday, August 18, 2012 - link

    It seems the 7950 trades blows with the reference GTX660Ti. It wins some and looses some. However, it suffers some pretty massive loses in games like Battlefield 3 and Shogun 2. However, it seems the 7950 has better resilience at higher resolution. Overall, it comes up short though, so it is a good thing AMD released the update. The 7950B, overall, seems to maintain a small margin of victory over the overclocked variants of the GTX660Ti, thus saving face as a high end card (even if barely). It will be interesting to see how well the 3GB GTX660Ti does. It doesn't have the asymmetric memory penalty that the 2GB variants have. Reply
  • n0x1ous - Tuesday, August 14, 2012 - link

    u mad bro? Reply
  • hechacker1 - Tuesday, August 14, 2012 - link

    With the voltage already set higher in the bios, I wonder how these cards overclock?

    I know they are low quality parts, but considering not every single one of these requires 1.25V, I bet some of them overclock really well. Plus you wouldn't have to resort to driver/bios hacks to get it running at a higher voltage.

    But I guess then you might run into the PSU limit of trying to power it.
    Reply
  • CeriseCogburn - Wednesday, August 29, 2012 - link

    Where's the big rant about amd's failing gpu production where their cores need extra voltage for a tiny OC ?
    LOL
    I thought we'd get ten pages of the "astute" amd fans who spent three years+ bashing nVidia's "process" since the - heck 4-5 years since the 200 series.
    Where did they all go when the amd crapship needs a giant voltage bump to come out barely above where it wsa before and WAY BELOW WHERE ALL THE AMD FANBOYS HAVE BEEN CLAIMING FOR ALMOST A YEAR IT PASSES ON OLDER LOWER STOCK VOLTAGE...
    Where's all the whining and moaners and laughing fools screaming housefire on amd's failing fire hot core production ?
    I guess they... I was going to say finally went looking for a job so they wouldn't have to whine about price all the time but the economy clearly nixes that...
    I guess I'll have to fill in for them...
    amd = 1.7% good cores
    amd= CEO's fled the housefires
    amd= another stupid move
    amd= no problem our fanboys will suck down and swallow the koolaid
    Reply
  • martyrant - Tuesday, August 14, 2012 - link

    It's pretty obvious why this is happening the way it is (and when), and why there is no name change. They're getting ready to compete with the gtx 660 that releases this month (supposedly) and instead of the time and money it would take to create a new card, they devised this BIOS "hack"/"update" as a response.

    Would like to see a GTX 660 review from here, as I think they're starting to pop up around the web (saw at least one already). While typically an ATi fanboy since the 9700 series (my first was a 7500, which predates that a bit) I've noticed that this round in the ring it seems to be in favor of nVIDIA (and while I've had a few great nvidia cards, I've most lately become accustomed to being able to use eyefinity).

    Seeing as nVIDIA now has 3+1 displays, I might give it a shot this time around--still waiting to decide on what to upgrade to--but being able to use up to 6 is quite nice in my opinion. With the price drop of the 7970 now it makes a lot of sense compared to the 670/680, but with the 660 coming into play soon we may see a new price/performance king. I just read a ton of horror stories on AMD's driver support for their top tier cards these days...

    Anyway, 660 review please!
    Reply
  • RussianSensation - Wednesday, August 15, 2012 - link

    HD7970 is now faster than 670 and 7970 GE is faster than the 680 overall:

    http://www.computerbase.de/artikel/grafikkarten/20...

    Take a 7950 and overclock it to 1.1ghz and see what happens to an overclocked 660Ti with MSAA enabled.
    Reply
  • CeriseCogburn - Wednesday, August 29, 2012 - link

    " I just read a ton of horror stories on AMD's driver support for their top tier cards these days..."

    LOL - reality bites
    Reply

Log in

Don't have an account? Sign up now