Monday, August 12, 2013

Review: AMD Radeon HD 7990

Review: AMD Radeon HD 7990

Review: AMD Radeon HD 7990


Things are getting a tad stagnant in the graphics card market at the moment. Sure, we're still seeing new graphics cards on a fairly regular basis, but they're mostly re-badged, re-released or re-tweaked versions of existing hardware.

Whether we're talking about ultra-enthusiast class graphics cards like the Nvidia GTX Titan or lower-end parts like the AMD HD 7790, we're not really seeing new technology - just different ways to package it for the consumer.

And here we have another brand new card that we've actually already seen elsewhere in some guise or another. This time it's AMD getting in on the ultra-enthusiast segment, having given its AIB partners a little time in the sun with their own dual-GPU, Tahiti-based cards.

"We've helpe d our partners with these products," said AMD's Devon Nekechuk at a recent briefing. "We actually put a lot of focus helping them develop parts of these cards. We've designed parts of the Ares II and Devil 13 in partnership with Asus and Powercolor. We want to jump in this game, too."

AMD is now releasing its own spin on the CrossFireX card, code-named Malta - the Radeon HD 7990. Yes people, we're talking about a new graphics card, and at £863 (about AU$ 1,355, US$ 1,300) it actually costs more than a GTX Titan.

But that should come as no surprise, given the fastest graphics card in town, Asus' dual-GPU Ares II, costs around £1,200 (about AU$ 1.885, US$ 1,810) on its own. If AMD's Radeon cards are sitting atop the graphics card tree, why then is AMD so keen to throw its own version into the mix, especially as it's already helped design parts of its partners' cards?

"The core of this thing is that we set out to add to the family of the world's fastest graphics card. We wanted to create another product worthy of the HD 7990 brand to make sure we can cater to that market of people who don't buy graphics cards for utilitarian purposes," said Nekechuk. "They really want to create a Ferrari or a Lamborghini of a PC. They have that emotional attachment and they want the ultimate graphics card."

So, we're back to manufacturers banging the form-over-function drum, claiming people with the cash for ultra-enthusiast cards aren't necessarily after the outright fastest card, but want the best experience of ownership.

This isn't a persuasive argument when it comes to multi-GPU cards. With the vagaries of CrossFireX and SLI, you're almost guaranteed to have to get your hands dirty fixing multi-GPU problems with the latest games at some point, and single cards packing in a pair of GPUs tend to suffer more problems than most.

Serious hardware


For all Nekechuk's talk about not going after the somewhat utilitarian concept of speed at all costs, AMD has included some serious hardware at the heart of this new card.

AMD Radeon HD 7990 without cooler

As you would expect from its partners' existing HD 7990 designs, there's a pair of Tahiti XT GPUs burning away below those chunky heatsinks, and AMD has apparently been hoarding the fastest chips off the production line for its baby. "[We've been] putting aside the best of the best HD 7900 series parts and saving them for the HD 7990s," said Nekechuk. "So these are the lowest power parts - these are the fastest parts."

And these parts are given a base clock of 950MHz, though with the extra boost AMD has created, aping Nvidia's GPU Boost, they generally knock around the 1GHz mark in most tests. There's also a healthy 6GB chunk of GDDR5 memory split between the GPUs to make up the card's framebuffer.

The VRAM clocks in at 6Gbps, as has become standard with high-end graphics memory. AMD reckons that gives them over 500GB/s of bandwidth for shunting data between the GPUs, "to really cope with those ultra high-resolution, ultra-high framebuffers."

To keep the GPUs talking clearly, AMD has also jammed in the latest PLX PCIe chip into the card, which offers some 48 lanes of PCIe traffic. That gives the card almost 100GB/s of inter-GPU bandwidth, perfect when they're talking with each other or communicating outside to the system bus. And when you're jamming in a pair of the fastest cores AMD can manufacture, you're going to have to think pretty darned hard about the cooling of this multi-GPU card.

Thankfully, that's something AMD has spent a good chunk of time on, and that's mostly down to the impressive engineering Nvidia put into the GTX Titan. "Nvidia - I wont do this very often - I'll give them credit on the Titan: they made a quiet card," said Nekechuk. "But that just gave me a target. I'm not going to sit idle - I'm going to look at that Titan and say: 'They did a good job. I can do better.'"

And AMD has done a very good job. On our test rig, the water pump in the closed-loop CPU cooler was making all the noise - even when we had the GPUs at 100 per cent load.

I have to say, it doesn't look like much on the surface. There are three shallow fans spinning atop a mass of copper piping and aluminium heatsinks. But the HD 7990 resolutely sticks around the 80ºC mark when it's being really pushed, and even then it stays incredibly quiet.

It's by no means silent, but AMD has spent time working on the tone of the sound it produces when the fans are spun all the way up. You can hear it (when the water pump shuts up), but the gentle rush of air has none of the whine or harshness that you get from standard HD 7970 GHz cards or even the GTX 690.

AMD has also managed to keep the impressive cooling down to a dual-slot array, smaller than the triple-slot beasts we've already seen.

Performance and benchmarks

Game on?

Ah, but what of performance? Given everything AMD has said about making a desirable card, offering the best experience above all other objectives, the performance is pretty damn impressive for a single-PCB/multi-GPU card.

AMD Radeon HD 7990

The first and perhaps most important thing to say is that it beats the GTX 690 and GTX Titan in our performance metrics almost across the board. The only place where Nvidia held sway was in the Batman: Arkham City test, where Nvidia generally performs better.

Even more impressive is the fact that it stays above both the Nvidia cards in terms of the minimum recorded frame rate, too - and that's always a good indicator of how smooth a gaming experience you're going to get out of your rig.

What this card doesn't do is beat a CrossFireX pairing of twin HD 7970 GHz edition cards. That setup is over Â£150 (about AU$ 235, US$ 225) cheaper, making the HD 7990 a bit of a tough sell. That's why we had all the talk from Devon Nekechuk about not going for the utilitarian option - if you're after sheer performance, that CrossFireX pairing wins.

Where they fall down is experience - w hen pushed to their limits, a pair of HD 7970 GHz cards make one hell of a racket - but they're blisteringly quick and smoother than this HD 7990. So, this HD 7990 doesn't win the performance battle.


Peak platform power draw
100 per cent GPU: Watts: Lower is better

AMD HD 7990: 615
NVIDIA GTX 690: 528
2X AMD HD 7970 GHZ: 700

DirectX 11 gaming performance
Batman: Arkham City: Frames per second: Higher is better

AMD HD 7990: 103
NVIDIA GTX 690: 109
2X AMD HD 7970 GHZ: 99

Crysis 3: Frames per second: Higher is better
AMD HD 7990: 48
NVIDIA GTX 690: 42
2X AMD HD 7970 GHZ: 55

DirectX 11 tessellation performance
Heaven: Frames per second: Higher is better

AMD HD 7990: 43
NVIDIA GTX 690: 42
2X AMD HD 7970 GHZ: 47

DiRT Showdown: Frames per second: Higher is better
AMD HD 7990: 116
NVIDIA GTX 690: 66
2X AMD HD 7970 GHZ: 117

Max Payne 3: Frames per second: Higher is better
AMD HD 7990: 57
NVIDIA GTX 690: 54
2X AMD HD 7970 GHZ: 58



As effective as the cooling is, The AMD Radeon HD 7990 is never going to have the premium aesthetic of the GTX Titan. In graphics card terms, it looks like a super car - it's practically got alloys.

And if we take straight-line performance out of the equation and go for that experience angle, a multi-GPU card is never going to be able to compete against a simple, single-GPU card - especially one that's a little cheaper and only a bit slower in most cases.

Sadly, the HD 7990 is one of the flakiest c ards we've tested in a long while. We were finally able to coax some impressive performance figures out of it, but only after a good long while of sometimes only having a single GPU turning up to the benchmarking party. This is no doubt down to the early drivers we've had to use for pre-release testing and not the hardware itself, but that's a plain reminder of the vagaries of multi-GPU gaming.

When you fire up a new game on your CrossFireX or SLI rig, you'll always be wondering whether one or other of your GPUs has gotten confused and wandered off somewhere else. As impressive a feat of engineering as this beast is, there are faster, smoother and cheaper graphics arrays available, and much better enthusiast experiences to be had elsewhere.


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