AMD Radeon HD 7950 Review Feat. Sapphire & XFX: Sewing Up The High-End Marketby Ryan Smith on January 31, 2012 9:02 AM EST
Announced late last month and shipping 3 weeks ago, AMD kicked off the 28nm generation with a bang with their Radeon HD 7970. Combining TSMC’s new 28nm HKMG process with AMD’s equally new Graphics Core Next Architecture, AMD finally took back the single-GPU performance crown for the first time since 2010 with an all-around impressive flagship video card.
Of course AMD has always produced multiple video cards from their high-end GPUs, and with Tahiti this was no different. The second Tahiti card has been waiting in the wings for its own launch, and that launch has finally come. Today AMD is launching the Radeon HD 7950, the cooler, quieter, and cheaper sibling of the Radeon HD 7970. Aimed right at NVIDIA’s GeForce GTX 580, AMD is looking to sew up the high-end market, and as we’ll see the Radeon HD 7950 is exactly the card to accomplish that.
|AMD GPU Specification Comparison|
|AMD Radeon HD 7970||AMD Radeon HD 7950||AMD Radeon HD 6970||AMD Radeon HD 6950|
|Memory Clock||1.375GHz (5.5GHz effective) GDDR5||1.25GHz (5GHz effective) GDDR5||1.375GHz (5.5GHz effective) GDDR5||1.25GHz (5GHz effective) GDDR5|
|Memory Bus Width||384-bit||384-bit||256-bit||256-bit|
|Manufacturing Process||TSMC 28nm||TSMC 28nm||TSMC 40nm||TSMC 40nm|
As has been the case for AMD since the 5000 series, AMD has gone with a two-pronged approach to binning and cutting down their flagship GPU for their second-tier card. The first change is an across-the-board reduction in clockspeeds, with the core clock being dropped from 925MHz to 800MHz and the memory clock being dropped from 5.5GHz to 5GHz. The second change is that the shader count has been reduced from a full 2048 SPs to 1792 SPs, accomplished by disabling 1 of the GPU’s 8 CU arrays and allowing AMD to use Tahiti GPUs with a defective CU array that would have never worked in the first place.
No other changes have been made, a particularly important consideration since it means all 32 ROPs and the 6 64bit memory channels are still in place. Altogether this gives the 7950 86% of the ROP throughput, 75% of the shader and texture throughput, and 91% of the memory bandwidth of the 7970. This should put the 7950 in direct competition with NVIDIA’s GeForce GTX 580, which typically trails the 7970 by a similar degree. Otherwise compared to the 6000 series, this makes the core performance gap between the 7950 and 7970 a bit bigger than between the 6970 and 6950, while the memory bandwidth gap is identical.
The tradeoff of course on a second-tier part is that while performance has been reduced so has power consumption. Just as with the 7970, the 7950 takes after its 6000-series predecessor, shipping with a 200W maximum board power limit. With the 7000 series AMD has not been publishing any kind of typical power numbers and thereby making the board power limit the only number they publish, but also making for a far more accurate TDP than past estimated TDP numbers as it’s an absolute limit. For gaming scenarios you’re almost always looking at less than 190W power consumption, though the spread between typical power and the PowerTune cap is not as wide on the 7950 as it was the 7970. Meanwhile for idle power consumption AMD is not providing an official number there either, but with the use of power islands the difference in idle power consumption between various core configurations has been virtually eliminated. Idle TDP should be 15W, while long idle is 3W.
In a bit of an unusual move for AMD, for the 7950 they are doing away with reference designs entirely. All 7950s will be custom to some degree—the first run will use a partner’s choice of cooler alongside a new PCB from AMD specifically for the 7950, while in the future partners will have the option of going fully custom. Furthermore partners will be shipping factory overclocked parts from right out of the gate, and at this point we’re not even sure just how many models will actually be shipping at stock clocks; neither MSI or Sapphire have a stock clocked card as part of their lineup. Overall at the low-end we’re seeing overclocked cards shipping as low as 810MHz, while 900MHz is particularly common at the high-end.
The use of customized factory overclocked cards is not unusual for AMD’s lower-end cards, but this is the first time we’ve seen AMD’s partners launch factory overclocked parts out of the gate like this, and it’s the first time we’ve seen AMD launch a part over $200 without a reference cooler. As a result the 7950 will be a true Your Mileage May Vary situation, with the gaming performance and physical performance characteristics depending heavily on how a partner has configured their card.
|Radeon HD 7950 Partner Specification Comparison|
|AMD Radeon HD 7950 (Stock)||Sapphire HD 7950 Overclock Edition||XFX R7950 Black Edition Double Dissipation|
|Memory Clock||1.25GHz (5GHz effective) GDDR5||1.25GHz (5GHz effective) GDDR5||1.375GHz (5.5GHz effective) GDDR5|
|Memory Bus Width||384-bit||384-bit||384-bit|
|Manufacturing Process||TSMC 28nm||TSMC 28nm||TSMC 28nm|
For the launch of the 7950 AMD shipped us a pair of internal reference cards built on the 7970 PCB and cooler. Since no one will actually be shipping a card like this—although they technically could if they wanted to—we also went looking for partner cards, which XFX and Sapphire provided. The XFX R7950 Black Edition Double Dissipation and Sapphire HD 7950 Overclock Edition are far more representative of what we’re actually going to see on the market; factory overclocks aside, both use open air coolers, just as with every other 7950 card we’ve seen the specs for ahead of today’s launch. Given the lack of any cards using fully exhausting blowers, it would appear that AMD and their partners have become particularly comfortable with open air coolers for 200W cards.
Last but not least of course, is pricing. AMD is continuing their conservative pricing strategy of trying to price their cards against existing competitive cards, rather than using the cost savings of the 28nm process to bring down prices across the board. As a result the 7950 is priced at $449, $100 below the 7970 and almost directly opposite the cheapest GeForce GTX 580s, making the 7950 a de facto GTX 580 competitor. This pricing strategy seems to have worked well for the 7970—cards are still selling at a brisk pace, but the shelves are rarely completely bare—and it looks like AMD is going to continue following it while they can. Meanwhile the fact that the 7950 is an entirely semi-custom lineup means that pricing is going to be equally variable, with high-end factory overclocked cards such as the Sapphire and XFX going for $479 and $499 respectively.
|Winter 2011 GPU Pricing Comparison|
|$750||GeForce GTX 590|
|Radeon HD 6990||$700|
|Radeon HD 7970||$549|
|Radeon HD 7950||$450+||GeForce GTX 580|
|Radeon HD 6970||$350||GeForce GTX 570|
|Radeon HD 6950 2GB||$250|
|$240||GeForce GTX 560 Ti|
|Radeon HD 6870||$160|