Asus AMD Radeon HD 7790 DirectCU II OC full review

Graphics card watchers have been on tenterhooks waiting for the first glimpse of AMD's new HD 8000 series. The 7790 clearly isn't that. What it is, though, is a cunning twist on the existing 7000 cards, and one that offers strong competition to nVidia's price-conscious 650 range.

See: more graphics card reviews.

The launch of the new Boost has rather stolen AMD's thunder though, and it's a shame that the company couldn't have released the 7790 a few months earlier.

There's nothing particularly radical about the 7790, although it does play host to a new processing chip, codenamed Bonaire, a smaller and more compact take on the Cape Verde.

Given the model name, the most obvious point of comparison would be the Radeon HD 7770. And it's true that there are many similarities. In some areas, though, the 7790 even approaches the pricier 7850 in specifications.

Asus AMD Radeon HD 7790 DirectCU II OC: Specifications

In their factory-specified versions, both the AMD Radeon HD 7770 and 7790 offer the same 1GHz core-clock speed, although Asus has added a tiny 75Hz boost. This isn't a massive difference, but is complemented by an increase in texture units - from 40 on the 7770 to 56 here. That adds up to a texture fill rate of 60.2GTps, a more than 50% increase on the 40GTps of the 7770.

It still leaves it a distance behind the 70.3GTps of nVidia’s GTX 650 Ti Boost, though.

The Asus 7790's memory-clock speed of 1600MHz (itself a 100MHz increase on the factory-specified 7790) gives it a massive advantage over the 1125MHz of the standard 7770. Take into account the GDDR5 memory, and the effective figure of 6.4GHz is a huge jump on the 7770's 4.5GHz. It even beats the 650 Ti Boost's figure of 6008MHz.

However, while nVidia was smart enough to kit out the Boost with an expanded 192-bit memory bus, the 7790 is saddled with the same 128-bit version as the lowly 7770. This is quite a significant move, as low memory bandwidth tends to choke much the potential speed of these lower-priced cards.

The 7790's bandwidth figure of 102.4GBps is impressive compared to the 72GBps of the standard 7770. However, it pales when set against the 650 Ti Boost's massive 144.2GBps.

There are some spec-chasing victories elsewhere for the 7790, and its healthy complement of 896 shader cores is significantly better than the 768 of the 650 Ti Boost (or the mere 640 of the 7770); but it remains to be seen how costly that 128-bit memory interface proves.

The 7790 is pleasingly light on power. Its 85W TDP is nearly 50W below the 650 Ti Boost's figure of 134W. In real-world testing, we measured the difference at around 38W, but the 7790 is certainly low in power requirements and noise output.

Asus AMD Radeon HD 7790 DirectCU II OC: Performance

In performance, the bottlenecks proved a little too much for even the tuned-up Asus AMD Radeon HD 7790 DirectCU II OC 7790, as it remains several frames behind the GTX 650 Ti Boost in most areas.

In Crysis 2 it produces figures of 26.6 and 18.9fps at the largest display sizes (1900 x 1200 and 2560 x 1600). These results were almost three frames ahead of the Radeon 7770's, but the 650 Ti Boost was significantly ahead again, on 30.5 and 21.1fps respectively.

Move onto an easier set of tests, and the gap only increases. In Stalker: Call of Pripyat, for instance, the 7790's figures of 54.6 and 29.8fps were a long way adrift of the 650 Ti Boost's 65.9 and 41.3fps.

The gap was marginally closer in Battleforge (where 51.5 and 28.0fps for the 7790 go up against the Boost's numbers of 59.8 and 37.1fps), but it’s still sizeable.


Asus AMD Radeon HD 7790 DirectCU II OC: Specs

  • AMD Radeon HD 7790
  • 1GB GDDR5
  • 1GHz core clock (1075MHz Boost)
  • 1600MHz memory clock (6400MHz DDR effective)
  • 400MHz RAMDAC
  • 12-8bit memory interface
  • 896 stream processors
  • texture units
  • ROP units
  • PCI-E interface
  • DirectX 11
  • 2x DVI, 1x HDMI
  • 1x DP
  • 1x 6-pin PSU connector needed
  • 3-year warranty

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