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
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


View All Comments

  • silverblue - Wednesday, August 15, 2012 - link

    The point being - why spend $400 when you can save a hundred and overclock your card to the same speed. What if a specific card performs perfectly fine for your needs - why buy its faster brother?

    And less of the "retarded", please... all credibility gets blown out of the water when that particular gem pops up. Thanks.
  • Sufo - Wednesday, August 15, 2012 - link

    Not entirely convinced that's what OP was getting at. You make a valid enough point, however it kind of goes without saying that if a cheaper card performs to the level you require then that is the card you should buy - I'm not sure we've learnt much new here.

    As for using language such as "retarded" - if it diminishes my credibility then so be it. You can either digest the points within the post and take them for what they are, or you can read them, feel that they were totally reasonable then throw them out the window as soon as you encounter some phrasing aggravating to your delicate sensibilities. You *could* do this, but ofc it would make you a retard.
  • CeriseCogburn - Wednesday, August 29, 2012 - link

    He is. He brainfarted again. He said the same crap as the other tard, but for some reason, probably the retardation, he had to say it. Reply
  • CeriseCogburn - Wednesday, August 29, 2012 - link

    " The point being - why spend $400 when you can save a hundred and overclock your card to the same speed. "

    Are you RETARDED TOO ?
  • Frallan - Wednesday, August 15, 2012 - link


    Well wonderful 1/16th of a boost on the normal cards but still no 7950M what is AMD doing?
  • CeriseCogburn - Wednesday, August 29, 2012 - link

    Clearing out crap cores and trying to STOP the endless crashing at stock their cards suffer from.
    Think "stability voltage tweak" disguised as an "upgrade".
  • smithrd3512 - Wednesday, August 15, 2012 - link

    Its a very impressive card. I am curious what to see what the 7990 Radeon can do when it comes out this fall. Reply
  • tcool93 - Wednesday, August 15, 2012 - link

    I get so sick and tired of all the Nvidia fanboys who post their crap anymore.

    Funny how overclocking a card is now a big deal, yet its just fine when Nvidia sells overclocked cards, or uses proprietary game benchmarks to benefit their own cards.

    Nvidia is a thug run company, just like their users are.

    And if the AMD cards can overclock (and they do overclock by a lot), why not raise it. But no, the Nvidia fanboys can't have that, because it might make their cards not look so good.
  • RussianSensation - Wednesday, August 15, 2012 - link

    Remember when EVGA GTX460 FTW 850mhz card was for sale on Newegg? imo that was fair to include in the HD6870 review since the 460 is a card a user can buy. But now that 7950 is for sale with 880-950mhz factory clocks (MSI TF3, Gigabyte Windforce 3x, Sapphire Dual-X), those cards are "cheating" and now 460's famous overclocking isn't applicable to the 7950? Interesting. Next thing we'll hear that MSAA is outdated and obsolete and that real gamers use TXAA..... Reply
  • raghu78 - Saturday, August 18, 2012 - link

    Exactly. These reviewers think we are all fools to believe a GTX 660 Ti competes with HD 7950 and overclock it further with voltage tweaking .

    clock for clock HD 7950 is 3 - 5% slower than HD 7970. its easily proven by comparing OC benchmarks of anandtech itself.

    So even if you overclock HD 7970 the relation holds true. HD 7970(1250) would be 3 - 5% faster than 7950 (1250). So people who bring the whole " the faster card can overclock too" are just silly. The problem is reviewers can't do anything which will piss off Nvidia. So they play by the 800 lb gorilla's rules. No reviewer has the guts to take a factory overclocked HD 7950, HD 7970, GTX 670, GTX 680 and push it to their maximum speeds with voltage tweaking. This will clearly prove that the HD 7950 is the best value for you money and it will make the people who purchase GTX 680 cards for USD 600 look silly. Unfortunately in the real world Nvidia holds too much power and influence. so no reviewer will do that.

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