AMD Radeon HD 7970 graphics card the fastest single GPU around

By Muhammad Faisal 0 comments
AMD Radeon HD 7970 the fastest single GPU graphics card aroundAMD has blinked first and has released its new graphics card architecture just before Nvidia. So here it is, the Southern Island AMD Radeon HD 7970 and, for the time being, it's the fastest graphics card around.

It's a brave move by AMD to bring out a radically different graphics design spec, compared with its previous vector processors, just after it brought us a brand new CPU architecture. Especially given the depressing failure of the AMD FX chips.

We've seen little bits from AMD about its new architecture - the plainly named Graphics Core Next - before, but now it's humming away in test bench and throwing pixels and polygons around high-res screens without a care in the world.

Well, maybe the AMD Radeon HD 7970 does have some cause for concern considering Nvidia is set to launch its newest graphics card architecture, code-named Kepler, by the spring.

It could also explain why the timing of this release is so odd. AMD decided to effectively launch the AMD Radeon HD 7970 just three days before Christmas, a notorious deadspot in technology news.

Speaking with AMD's partners, though, found they weren't allowed to release overclocked graphics card until a while after launch, so all AMD Radeon HD 7970 graphics card with new stickers.

That means much of their thunder was stolen by the pre-Christmas unveiling. And even thunder remained was quickly silenced by the festive period.

So, like a cabinet minister in a time of crisis, was AMD trying to bury the launch of the AMD Radeon HD 7970?

Maybe it realises the market for $791 graphics card is absolutely minute. Maybe the forthcoming Radeon HD 7950 is the card that it wants to really concentrate on. Maybe it just wanted to make sure us tech journos had to work right up to Christmas.

Whatever the real reason for this staggered launch, it's time we took a proper look at what makes the AMD Radeon HD 7970 tick.

Make-up

In terms of its actual make-up, it's a fairly different beast to the previous Cayman GPU-powered HD 6970.

This graphics card represents a new direction in GPU tech for AMID as well as a new production process and GPU technologies.

In terms of firsts, AMD has them all pretty much nailed with the AMD Radeon HD 7970. It's the first GPU to be built with miniscule 28nm transistors, the first DirectX 11.1 graphics card and first of official PCI Express 3.0 component too.

Of those, the one of real interest is the 28nm die shrink that comes with this new Tahiti core. The Tahiti GPU is going to be the chip powering the top-end cards and that in turn is built on the new Graphics Core Next architecture.

The whole HD 7000 series also goes by the name of Southern Islands, hence the Tahiti tag.

That die-shrink means that it can jam more components into a smaller chip footprint, and that should mean more power to you.

And compared to the number of 40nm transistors in the Radeon HD 6970 - a paltry 2.6 billion - AMD it has done a good job of squeezing more into the AMD Radeon HD 7970. This graphics card has 4.3 billion transistors in the GPU itself. That is a frightening number - and AMD has plenty more of those for the AMD Radeon HD 7970.

AMD's claimed compute performance for the Tahiti XT GPU inside the AMD Radeon HD 7970 is one such number. At 3.79 TFLOPs there is some impressive number crunching capabilities buried inside this chip. All it needs is the software to take advantage of it.

  Graphics Card represents a new direction in GPU Tech for AMD

The compute performance has been the driving factor in the change from Northern Islands to Southern Islands, and fom the traditional vector style processor to the scalar processor that makes up this new GPU.

Previously AMD had focused most of its silicon towards the goal of making a card specifically for graphical processing, leaving the more ephemeral notion of general purpose GPU computing to Nvidia its CUDA cores.

So it put all its eggs in the four-way vector processor architecture basket. Essentially that meant sorting out single instructions into batches before firing them down the GPU pipelines. It was a much more elegant solution and for doing fixed graphical processing it was incredibly efficient. The resulting HD 4xxx thru 6xxx series cards were great pixel pushers at impressively lower power requirements than their peers.

Now, though, AMD wants a slice of the GPU pie and as such has shifted to a similar scalar architecture to that used by long-time rivals Nvidia.

That means it's going for a more brute force approach, which involves having a large number of simple processors in an array, giving them each one thing to work on at a time until all the instructions have been completed.
AMD Radeon HD 7970 graphics card
The Graphics Core Next architecture is built of Compute Units, which are similar to Nvidia's streaming microprocessors it introduced with the Fermi architecture.

The Tahiti XT GPU in the HD 7970 is built up of 32 of these Compute Unites, which are essentially self-contained processors that can act independently of the whole.

Inside are four vector units, and in each of those are 16 unified shaders, stream processors or Radeon Cores - depending on who you talk to. That means in the full Tahiti XT you'll find 2,048 shaders and, compared to the 1,536 shaders of the HD 6970, that's a fair mark up.

You're looking at a 30 percent improvement over the NVIDIA GTX 580

It's this combination of four-way vector processing and scalar architecture that AMD hopes will push its Tahiti-based GPUs to the top of the graphics card pile.

Though it's not just the number of Compute Units that makes the difference in performance terms - the actual coe clock of the Radeon HD 7970 is far higher than previous cards too. At 925MHz out of the box, it's a chunk faster that the 880MHz of the Radeon HD 6970.

AMD Radeon HD 7970 graphics card Performance

Now we come to the crunch - the performance of this brand new slice of graphical silicon goodness. It's quick. Well, pretty quick.

The HD 7970 beats the Nvidia GTX 580 hands down when it comes to raw graphics-chomping, pixel-pushing, polygon-smashing performance. In all the gaming benchmarks the HD 7970 has the Nvidia card in second place, especially when you look at the demanding Heaven 2.5 and Crysis 2 benchmarks. With both those benchmarks you're looking at aroung a 30 percent improvement over the Nvidia GTX 580

Those are the best case scenarios, though, since the performance benefits in the other titles are much less pronounced, sitting between 13 percent and 20 percent frame rate improvements.

When it comes to the previous generation - the venerable Cayman-powered HD 6970 - things look more impressive. The HD 7970 posts a 65 percent improvement over the older card in the tessellation-heavy Heaven 2.5 benchmark. That's the highest performance increase, but at worst it's around 25 percent faster.

This is all before you start waving the overclocking stick around. And boy, does this chip overclock. In fact, ran into the limits of the AMD OverDrive software rather than the limits of the hardware itself. Pushed the card all the way up to 1,125MHz on the core clock and 1,575MHz on the memory clock.

With those numbers the performance increase over the GTX 580 and HD 6970 are way more pronounced, with the HD 7970 beating the previous generation by up to 80 percent. When overclocked too it gives the previous generation of dual-GPU cards, the GTX 590 and HD 6990, a good run for their money. The GTX 590 had the highest score of 33fps while the HD 7970 come in just behind 32fps. The HD 6990 actually lags behind it with 29fps.

It's not just all about the raw performance figures though, because AMD has made a lot of effort with the power requirements of the Radeon HD 7970, especially when running in idle mode and with the screen off. The ZeroCore Power technology means when the screen turns off and the machine goes into the 'long idle' state - where the computer is still running but there is nothing being updated on the screen, so the panel goes to sleep - there is only a single chip on the card that's still running.

That chip is there just to tell the computer there is still a card in the PCI slot and not to worry. The rest of the graphics card turns off completely, even the fan.

Lottery winner?

We've accounted for the architecture and performance of the AMD Radeon HD 7970, but there is one thing we haven't covered - the price. This is a key element of the graphics card battle and in the case of the HD 7970 may well be the thing that truly buries it. At approximately $791 it's, quite frankly, a ridiculously priced card.

It may well be the fastest single-GPU card currently available, but there is still little justification for the price. Apart from the fact that a chip with 4.3 billion transistors, running on a new production process, is going to be rather expensive to manufacture.

There's also the question of whether you really need the levels of graphical performance the HD 7970 offers. There are very few of out there running a monitor capable of the eye-watering resolutions of 2560 x 1600, so realistically a 1920 x 1080 resolution is going to be more likely. At that resolution the excellent $578 Nvidia GTX 580 is all the card you're going to need.

How much, we wonder, is the forthcoming dual-GPU version going to cost? $1,108? It's a shame, because if the card had come out at the same sort of price as AMD originally tagged the HD 6970 with it would have had a far better reception.

There are some good points about the HD 7970 the pricing cannot diminish however, and that's because they will be rolled out across the Tahiti line. That's the impressive ZeroCore Power tech. Being able to shut the GPU down almost completely when idle is a great feat of engineering, made doubly so when you bring in CrossFire setups.

When in CrossFire mode all the GPUs will be in use when you're gaming, but when you drop down to 2D desktop mode all GPUs bar the main card attached to the display, will shut down, fan and all.

That's impressive and means when you're using your monster rig in general computing tasks you're not going to require your own private Sellafield to power it.

The overclocking potential of the HD 7970 is likewise impressive. Well managed a huge overclock, which made question why it wasn't rated as the first 1GHz GPU out of the box. Got the answer from AMD's director of product management for discrete graphics, Zvika Greenstein, at a tech insight event for the Graphics Core Next products. "One of the things enthusiasts like to do with our cards is overclock them. They pay a premium for that," said Greenstein. "We can position the HD 7970 as the fastest graphics card in the market at the reference clocks, so we though that we might as well leave it to the end users."

In essence, AMD didn't need to push the silicon, since it's going to rely on the actual board manufacturers to that themselves. And they'll in turn charge end-users a premium for it.

The price may well be the thing that truly buries the HD 7970

If Nvidia's card is even more expensive than the HD 7970 then this card may start to look like good value. More likely the second tier Tahiti-powered card will be the card that is to recommend. Unfortunately the release of the HD 7950, for reasons unknown, has been knocked back a month. The cynic in me wants to say AMD is trying to squeeze as many sales out of this card as it can before the cheaper HD 7950 cannibalises them.

So again, it's another wait-and-see release - wait for Nvidia's Kepler card and see how much cheaper the HD 7950 is compared to this pricly ol' bast.

Vital Statistics
Price $762
Manufacturer AMD
GPU Tahiti XT
Production process 28nm
Core clock 925MHz
Memory clock 1,375MHz
Compute units 32
Stream processors 2,048
ROPs 32

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