Gigabyte GeForce GT 640 OC review full review

After the launch of powerful – but expensive – graphics cards like the nVidia GTX 680, it’s good to see nVidia starting to fill out its budget ranks. The nVidia GT 640 card uses a new GK107 chip as its foundation. Read more graphics card reviews.

From the model number, you might assume that the GK107 was more powerful than the GK104 used in the GTX 690, 680 and 670. In fact, it amounts to a smaller and much less complex piece of silicon. It’s still constructed using the all-important 28nm manufacturing process.

This Gigabyte version, the Gigabyte GeForce GT 640 OC, is quite an improvement on the standard nVidia GT 640. The core clock speed has been pushed up from 900MHz to 1050MHz. And the memory clock speed has been marginally increased from 891MHz to 900MHz. 

The memory used is only DDR3, so the effect of double-data rate RAM is merely to double this memory clock – the GT 640 runs at an effective rate of 1.8GHz. In graphics card terms, these figures are actually rather modest. 

Even with the enhancements, the Gigabyte GeForce GT 640 OC’s memory bandwidth is a mere 28.8GBps, thanks to the 128-bit memory interface.

With that big increase in the core-clock speed, the texture fill rate is boosted no end, but even here, the GT 640 OC can muster a mere 33.6GTps. With the standard 900MHz core speed, it would have produced an even less impressive 28.8GTps. 

To put these figures into perspective, the only marginally more expensive Gigabyte HD 7770 OC offers a texture fill-rate of 44GTps and a memory bandwidth of 80GBps.  

The latter, in fairness, is more the product of the 7770 OC using GDDR5 memory, but the end result is the same – the GT 640, even in its overclocked form, looks undercooked.

Gigabyte GeForce GT 640 OC: Performance

In practice, the Gigabyte GeForce GT 640 OC turned out to be very much below par. In BattleForge, the 640 scored 28.9 and 25.3fps at resolutions of 1680x1050 and 1900x1200 respectively. This compared with 31.3 and 27.5fps in the case of the 7750. 

Even with the higher clocked speed, it was still trailing the 7750 – itself available for considerably less. The differences didn’t vary much in Crysis 2, with the 640’s figures of 18.1 and 16.8fps comparing with the 7750’s 19.9 and 18.2fps.  

Stalker: Call of Pripyat saw the same thing again, and the 640’s figures of 28.5 and 25.0fps were once more inferior to the 7750’s 30.8 and 27.3fps.  

We stress that these differences come despite the higher clock speeds. You can buy non-overclocked versions of the same board, but despite costing around the same as the 7750, we suspect those would be several frames slower again. The only marginally more expensive 7770 is a long way ahead of the 640 on figures.

Gigabyte has done its best with unpromising hardware, and the outputs are interesting. While reference boards (and many retail versions) based on the GT 640 come with just two digital connectors, the Gigabyte GeForce GT 640 OC has HDMI and a pair of DVI ports, allowing three digitally connected displays to be used with nVidia’s Surround technology. 

Given the dearth of processing power, the card won’t be suitable for high-level surround gaming. However, if you’re prepared to keep detail settings down, it should be possible to use this card to play most games with additional screens. The card is also reasonably quiet, and barely registered on our sound meter.


Gigabyte GeForce GT 640 OC review: Specs

  • nVidia GeForce GT 640 OC
  • 2GB DDR3
  • 1050MHz core clock
  • 1800MHz memory clock (MHz DDR effective)
  • 400MHz RAMDAC
  • 128-bit memory interface
  • 384 stream processors
  • 32 texture units
  • 16 ROP units
  • PCI-E interface
  • DirectX 11
  • 1 x VGA, 2 x DVI, 1 x HDMI
  • 3-year warranty