AMD Radeon HD 7990

The new AMD Radeon HD 7990 dual-GPU graphics card is meant to challenge Nvidia at the top of the consumer graphics stack. The HD 7990 combines two HD 7970 GPUs on a single PCB and includes a huge number of bundled games. It's competitive?but exactly how competitive depends on which game you check and whether or not the title is optimized to run on more than one graphics card.

In one sense, the Radeon HD 7990 is actually a bit late to the party. Analysts expected the card to launch a year ago, after Nvidia debuted its own dual-graphics solution, the Nvidia GeForce GTX 690. AMD allowed board manufacturers like PowerColor to launch unofficial Radeon 7990s based on custom design work, but elected not to put an official stamp of approval on its own card. The Sunnyvale, CA-based company remained mum on the topic of whether it would introduce a new dual-core GPU, even after Nvidia launched the $1,000 Nvidia GeForce GTX Titan in late February. As of today, all that changes?the new, official Radeon HD 7990 is meant to compete with both the GTX 690 and GTX Titan at the $1,000 price point.

Design and Features
Spec-wise, the Radeon HD 7990 is a pair of Radeon 7970 GPUs (codename: Tahiti) on the same slab of silicon. Each GPU contains 2,048 stream processors, 6GB of GDDR5, and a 384-bit memory bus. Each GPU is clocked at 1,000MHz, with a 1,375MHz memory clock. The two GPUs communicate directly with each other via a 48-lane PCI-E 3.0 bridge chip developed by PLX.

There are several differences between the new official 7990 and the older PowerColor custom GPU. Clock speeds on the official card are slightly higher (1GHz compared with 925MHz) and the AMD card draws significantly less power. The old PowerColor solution required three 8-pin PCI-Express power connectors and used a three-slot GPU cooling solution. The Radeon HD 7990 has a two-slot cooler and requires just two 8-pin PCIe power connectors. Finally, there's the question of graphics ports. PowerColor's custom HD 7990 offered two DVI ports, two mini DisplayPorts, and an HDMI port. The Radeon HD 7990 has a single DVI port and 4x mini DisplayPorts. These differences imply that AMD spent some time optimizing the Radeon 7990's twin GPUs for lower power consumption before it deployed the cards.

Software is the other area where AMD is pulling out all the stops. Anyone who buys a Radeon HD 7990 will also receive the following games as part of the company's "Never Settle" bundled game promotion:

? Far Cry 3: Blood Dragon (upcoming)
? Crysis 3
? BioShock Infinite
? Tomb Raider
? Far Cry 3
? Hitman: Absolution
? Sleeping Dogs
? Deus Ex: Human Revolution

These aren't just titles someone in marketing plucked out of a hat; they're some of the best games released in the past 12 months. BioShock Infinite is the top-rated game on Metacritic, while Tomb Raider is in third place. Anyone looking to drop $1,000 on a new graphics card has likely played some of these games already, but the bundle is worth roughly $300 (as priced at Amazon). The Radeon HD 7990 wins the all-time "bundled goodies" competition, hands down.

Before we discuss the Radeon HD 7990's performance, we need to talk about its competition. AMD's new dual-GPU is facing down two separate products from Nvidia?the single-GPU supercomputing-derived GTX Titan, with 2,668 CUDA cores and 6GB of GDDR5, and the dual-GPU GTX 690. Like the HD 7990, the GTX 690 sports a pair of GK104 graphics processors on a single PCB connected by a high-speed link chip. Each Nvidia GPU has its own pool of GDDR5 (2GB each). The GTX Titan, of course, is its own animal. It's a single GPU with 75% more cores than a single GK104 GPU and a 6GB frame buffer.

When we reviewed the Nvidia GTX Titan, we noted that the card wouldn't automatically be faster than the Nvidia GTX 690 in every instance. There are times when a pair of graphics cards working in SLI is going to be faster than a single card. There are also times when the reverse is true. Splitting a graphics workload into two sections, offloading those sections, and then recombining the output take a certain amount of time.

Testing and Performance
Our performance comparisons were done using an Intel Core i7-3770K Ivy Bridge CPU, 16GB of DDR3-1600, a 256GB OCZ Vector SSD, and a 27-inch Asus VG278HE monitor at 1,920-by-1,080. The Nvidia GTX 690's performance was simulated using a pair of GTX 680s in SLI; tests have demonstrated that the performance delta between the two configurations is essentially nil. All of our tests were run at 1,920-by-1,080 with maximum details set. Multi-sampled antialiasing was activated when available and turned up to 8x if possible.

In the Civilization V Late Game View benchmark test, the Radeon HD 7990 turned in a score of 93 frames per second (fps), compared with the Nvidia GTX 680 SLI's 98fps and the 102.6fps for the Nvidia GTX Titan. The critically acclaimed BioShock Infinite was a win for the Radeon HD 7990?it hit 108fps, compared with 107 for the Nvidia GTX 680 SLI and 88 for the Nvidia GTX Titan. In Hitman: Absolution, the Radeon HD 7990 had a commanding lead at 85fps, compared with 49fps for the Nvidia GTX Titan and 58fps for the pair of Nvidia GTX 680s in SLI mode.

There were, however, cases when performance slipped the other way. In Diablo III, the Radeon HD 7990 hit 139fps, which wasn't as good as the Nvidia GTX Titan (221fps), but was better compared with 136fps for the Nvidia GTX 680s in SLI. Multi-GPU support is apparently the culprit?Diablo 3 takes minimal advantage of the second GPU. Batman: Arkham City is another game where the Nvidia GTX Titan won by a wide margin: 112fps versus 94.8fps for the Nvidia GTX 680 SLI and 73fps for the Radeon HD 7990. Later investigation proved that Batman: Arkham City doesn't support CrossFire, which leaves the game running on just one GPU.

Which card is "best," in other words, depends on where you look. Historically, Nvidia has done a better job than AMD at providing timely driver updates with multi-GPU support for the latest games, but that trend may no longer be accurate. Since AMD first launched the "Never Settle" program last fall, the company has been putting a great deal more effort into driver updates, multi-GPU support, and sponsoring high-profile games.

The Nvidia GeForce GTX Titan is still the fastest single-GPU card on the market, but if you're looking for a dual-GPU solution, the AMD Radeon HD 7990 is a worthy competitor. Its overall performance is comparable to the Nvidia GTX 690 or (or a pair of Nvidia GTX 680's in SLI), and it comes with a massive game bundle. If you've been out of the game market for several years and are looking to jump back in with a full suite of titles, the Radeon HD 7990 is a great way to do it.

Source: http://feedproxy.google.com/~r/ziffdavis/pcmag/~3/kFu3dlqqwB8/0,2817,2418092,00.asp

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