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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
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  • Ryun - Tuesday, August 14, 2012 - link

    I would rather AMD just lower the price of the 7950 as a consumer, but coming from their perspective it probably makes more sense to increase performance but keep the price the same. Reply
  • RussianSensation - Tuesday, August 14, 2012 - link

    Previous MSRP was $449.99, then $349.99 and now it's falling to $329.99.

    The thing is you don't have to get a reference 7950B with an overvolted BIOS. There are plenty of after market 7950 cards that can hit 1.1-1.15ghz with 1.15V for example. MSI TwinFrozr III and Gigabyte Windforce 3x 7950 cards come to mind and both can be purchased on Newegg, Amazon, Superbiiz for $320-330 or sometimes even $310. This way the consumer gets the best of all worlds:

    1) Upgraded cooling to reduce noise and better handle overclocking above 925mhz;

    2) Better binned Tahiti chips (esp. in the case of the TF3) that can overclock well on much lower voltage;

    3) The power consumption increase is a lot less dramatic with cream of the crop 7950 cards that can hit 1.1ghz+ with voltages way under 1.2V. It would make sense that the reference 7950B cards would get the worst possible Tahiti chips since reference design isn't really made for much overclocking headroom.

    It will be interesting to see how GTX660Ti compares since at 925mhz, HD7950 is roughly 5-6% behind the 7970 which is just 3-4% behind the 670.
    Reply
  • just4U - Tuesday, August 14, 2012 - link

    Ryan sort of leads readers to believe 7950 is well behind the 670. I'd always thought it was within a 5-10% margin and with these new incarnations would lessen the gap even more. Not that it matters. It's still (imo) 680 670/7970 then the 7950... and current prices reflect that. Reply
  • RussianSensation - Wednesday, August 15, 2012 - link

    Ya, that's because if you saw how the GPU Boost reacts, it doesn't stay pegged at 925mhz as would be the case with a manually overclocked 925mhz 7950. This is why the average increase in speed is only 5-6% on the 7950B as opposed to 10-12% you'd see on the regular 7950 manually overclocked to 925mhz. Reply
  • CeriseCogburn - Saturday, August 25, 2012 - link

    This card is a stupid amd brain fart, right ? I mean all you freaks claim all the amd fans OVERCLOCK or they wouldn't be buying these high end cards....
    So were you lying or is amd stupid as dirt ?
    Reply
  • raghu78 - Wednesday, August 15, 2012 - link

    well said. Factory overclocked cards like Sapphire HD 7950 950 Mhz edition have very good cooler design, enthusiast friendly features like Dual BIOS for aggressive overclocking and excellent binning. These cards overclock to 1150 Mhz or higher speeds with a bit of voltage tweaking. And here we are talking about completely moot points. clock for clock HD 7950 is 3 - 5% slower than HD 7970. As for performance GTX 670 and HD 7950 are competitive when overclocked. the Sapphire HD 7950 950 Mhz edition can be had for USD 350 at newegg. so generally HD 7950 has better price perf and similar overclocked performance. Reply
  • skgiven - Sunday, August 19, 2012 - link

    Good points.
    I don't see any place for this card in the existing market. It's basically competing with itself, or bespoke/non-reference manufacture versions of the card, and I don't think it compares well against those. Why annoy your partners by trying to elbow in an unwanted reference design?

    The extra speed really does come at a price, not cash but a 1.125 base Voltage. This is very high (we are talking about the same territory as the first HOT Firmi's), and an extra 25W is a lot. We have come to expect improved efficiency with refreshes, not a 12.5% increased power requirement for a mere 6% performance improvement. Just a bad card that looks even worse against the 660Ti's load power requirements. I would consider a manufacturer's bespoke implementation of a HD7950 but not this B grade effort.

    "It will be interesting to see how GTX660Ti compares since at 925mhz, HD7950 is roughly 5-6% behind the 7970 which is just 3-4% behind the 670".

    But which GTX660Ti? Although there is a sort of basic spec/reference model there is a huge range of GTX660Ti cards from 925MHz to 1033MHz (so far). That's a performance range of over 11% (or 13% if you go by boost clocks). Some even have higher clocked GDDR5 and some have 3GB instead of 2GB. So there is plenty of diversity/competition. Some performances of the 'superclocked' cards even pass a reference GTX670 (Portal 2).

    AMD need a proper refresh, to regain the lead, not a supped up reference card...
    Reply
  • Jamahl - Tuesday, August 14, 2012 - link

    I agree that the power difference makes this somewhat a double-edged sword.

    I disagree with one part of your conclusion however - having compared both in your bench - http://www.anandtech.com/bench/Product/598?vs=645 the 7950 is starting to look a bit closer to the gtx 670, don't you agree?

    it's only 12% behind at 1920x1200, and really that outlying battlefield result (34% faster on the 670) seems to be making a lot of the difference. Remove that one and it's 9% - then what will happen if you switch out Dirt 3 for Dirt Showdown? Not much in it all of a sudden.
    Reply
  • RussianSensation - Wednesday, August 15, 2012 - link

    Exactly. Also a lot of 7950s scale well past 1.1ghz and there are certain games not in the test bench that run well on AMD cards: Sniper Elite V2, Anno 2070, Bulletstorm, Serious Sam 3, SKYRIM with mods, Risen Dark Waters. Reply
  • bill4 - Tuesday, August 14, 2012 - link

    "Until such a time where the competitive landscape changes, the 7950 will continue to be well behind its next-closest competitor, GTX 670"

    Umm, yeah, and it's also well behind it in price too. Like, $80-$100. Comparing them is stupid, so why did you do it? Compare it to a 560 Ti or something if you just have to compare it to something from Nvidia. This thing will fight the 660 Ti, and guess what, it'll compete well!

    Reviewers really seem to have it out for AMD lately. I dont think Ryan does, I think it was just a clumsy review.

    This seems a little pointless, but by the same token so is Nvidia's boost and reviewers love that. The bottom line is 6% more on some bar graphs makes the 7950 look better to some buyers, and thats why they did it. Nvidia's cards are auto overclocking, so they were gaining an unfair advantage in "stock" reviews. No more.

    Nvidia started all this with their boost, I applaud AMD competing.

    BTW, zero mainstream reviewers have yet addressed the obvious and fundamental issue that Nvidia is (surely) cherry picking their review samples, which with boost means it is actually performing better than the cards the public will buy (the Way AMD's boost works it isn't the case for them). This amazes me, as it was literally the first thing that came to my mind when reading first reviews of Nvidia's new cards. Nvidia has the media in it's pocket.
    Reply

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