GeForce 9800 GX2 vs GeForce GT 640 DDR3

Intro

Compare all that to the GeForce GT 640 DDR3, which features GPU core speed of 900 MHz, and 2048 MB of DDR3 RAM set to run at 1782 MHz through a 128-bit bus. It also is comprised of 384 Stream Processors, 32 Texture Address Units, and 16 Raster Operation Units.

Display Graphs

Hide Graphs

Power Usage and Theoretical Benchmarks

Power Consumption (Max TDP)

GeForce GT 640 DDR3		65 Watts
GeForce 9800 GX2		197 Watts
	Difference: 132 Watts (203%)

Memory Bandwidth

Theoretically, the GeForce 9800 GX2 should be much faster than the GeForce GT 640 DDR3 in general. (explain)

GeForce 9800 GX2		128000 MB/sec
GeForce GT 640 DDR3		57024 MB/sec
	Difference: 70976 (124%)

Texel Rate

The GeForce 9800 GX2 will be a lot (approximately 167%) more effective at AF than the GeForce GT 640 DDR3. (explain)

GeForce 9800 GX2		76800 Mtexels/sec
GeForce GT 640 DDR3		28800 Mtexels/sec
	Difference: 48000 (167%)

Pixel Rate

If running with lots of anti-aliasing is important to you, then the GeForce 9800 GX2 is a better choice, and very much so. (explain)

GeForce 9800 GX2		19200 Mpixels/sec
GeForce GT 640 DDR3		14400 Mpixels/sec
	Difference: 4800 (33%)

Please note that the above 'benchmarks' are all just theoretical - the results were calculated based on the card's specifications, and real-world performance may (and probably will) vary at least a bit.

One or more cards in this comparison are multi-core. This means that their bandwidth, texel and pixel rates are theoretically doubled - this does not mean the card will actually perform twice as fast, but only that it should in theory be able to. Actual game benchmarks will give a more accurate idea of what it's capable of.

Price Comparison

Specifications

Memory Bandwidth: Bandwidth is the largest amount of information (in units of megabytes per second) that can be transferred past the external memory interface in a second. The number is worked out by multiplying the card's interface width by its memory clock speed. If the card has DDR memory, the result should be multiplied by 2 again. If DDR5, multiply by 4 instead. The higher the card's memory bandwidth, the faster the card will be in general. It especially helps with anti-aliasing, HDR and higher screen resolutions.

Texel Rate: Texel rate is the maximum texture map elements (texels) that are processed per second. This figure is calculated by multiplying the total amount of texture units of the card by the core speed of the chip. The higher this number, the better the graphics card will be at texture filtering (anisotropic filtering - AF). It is measured in millions of texels applied per second.

Pixel Rate: Pixel rate is the maximum number of pixels that the graphics card could possibly write to the local memory in a second - measured in millions of pixels per second. Pixel rate is worked out by multiplying the number of Render Output Units by the the card's clock speed. ROPs (Raster Operations Pipelines - aka Render Output Units) are responsible for filling the screen with pixels (the image). The actual pixel fill rate also depends on lots of other factors, most notably the memory bandwidth - the lower the memory bandwidth is, the lower the ability to reach the maximum fill rate.