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The card
Our GeForce GT 640 sample was kindly volunteered by Zotac. Here it is again, this time with its single-slot heatsink and fan still firmly attached:

Zotac is known for its amped-up, er, AMP! Edition cards, but this GT 640 couldn't be more sober. Its GPU runs at the standard 900MHz speed defined by Nvidia, and its two gigabytes of DDR3 memory are clocked at 891MHz, per the official specs. Zotac's cooler at least looks different from the one on Nvidia's reference design. The heatsink seems to have a fair bit more metal, which likely helps keep temperatures lower. The fan looks to be about the same size, though. It'll have to spin quickly to generate decent airflow, and the accompanying noise may not blend into the background whoosh of a quiet desktop PC. We'll look at noise levels in a bit.

The Zotac GeForce GT 640 sells for $109.99 at Newegg right now, which is in line with the prices of other GT 640 variants. We're going to compare it to a stock-clocked Radeon HD 7750 and MSI's slightly souped-up version of the GeForce GTX 550 Ti, the GTX 550 Ti Cyclone. For reference, vanilla 7750 variants sell for as little as $99.99 (or $89.99 after a mail-in rebate) at Newegg, and MSI's GTX 550 Ti Cyclone costs $124.99 (or $109.99 after MIR) at Amazon.

Our testing methods
As ever, we did our best to deliver clean benchmark numbers. Tests were run at least three times, and we reported the median results. Our test systems were configured like so:

Processor Intel Core i5-750
Motherboard Asus P7P55D
North bridge Intel P55 Express
South bridge
Memory size 4GB (2 DIMMs)
Memory type Kingston HyperX KHX2133C9AD3X2K2/4GX
DDR3 SDRAM at 1333MHz
Memory timings 9-9-9-24 1T
Chipset drivers INF update
Rapid Storage Technology
Audio Integrated Via VT1828S
with drivers
Hard drive Crucial RealSSD C300 256GB
Power supply Corsair HX750W 750W
OS Windows 7 Ultimate x64 Edition
Service Pack 1


  Driver revision GPU core
MSI GeForce GTX 550 Ti Cyclone GeForce 304.48 beta 950 1075 1024 (GDDR5)
Zotac GeForce GT 640 GeForce 304.48 beta 900 900 2048 (DDR3)
AMD Radeon HD 7750 Catalyst 12.6 beta 800 1125 2048 (GDDR5)

Thanks to Asus, Corsair, Crucial, Kingston, and Intel for helping to outfit our test rigs with some of the finest hardware available. AMD, Nvidia, and the makers of the graphics cards used for testing, as well.

Unless otherwise specified, image quality settings for the graphics cards were left at the control panel defaults. Vertical refresh sync (vsync) was disabled for all tests.

We used the following test applications:

Some further notes on our methods:

  • We used the Fraps utility to record frame rates while playing a 90-second sequence from the game. Although capturing frame rates while playing isn't precisely repeatable, we tried to make each run as similar as possible to all of the others. We tested each Fraps sequence five times per video card in order to counteract any variability. We've included frame-by-frame results from Fraps for each game, and in those plots, you're seeing the results from a single, representative pass through the test sequence.

  • We measured total system power consumption at the wall socket using a P3 Kill A Watt digital power meter. The monitor was plugged into a separate outlet, so its power draw was not part of our measurement. The cards were plugged into a motherboard on an open test bench.

    The idle measurements were taken at the Windows desktop with the Aero theme enabled. The cards were tested under load running Skyrim at its High quality preset.

  • We measured noise levels on our test system, sitting on an open test bench, using a TES-52 digital sound level meter. The meter was held approximately 8" from the test system at a height even with the top of the video card.

    You can think of these noise level measurements much like our system power consumption tests, because the entire systems' noise levels were measured. Of course, noise levels will vary greatly in the real world along with the acoustic properties of the PC enclosure used, whether the enclosure provides adequate cooling to avoid a card's highest fan speeds, placement of the enclosure in the room, and a whole range of other variables. These results should give a reasonably good picture of comparative fan noise, though.

  • We used GPU-Z to log GPU temperatures during our load testing.

The tests and methods we employ are generally publicly available and reproducible. If you have questions about our methods, hit our forums to talk with us about them.