GeForce GT 220 GDDR3 vs GeForce GT 640 DDR3

Intro

Compare all that to the GeForce GT 640 DDR3, which has a GPU core clock speed of 900 MHz, and 2048 MB of DDR3 RAM set to run at 1782 MHz through a 128-bit bus. It also is made up of 384 SPUs, 32 TAUs, and 16 Raster Operation Units.

Display Graphs

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Power Usage and Theoretical Benchmarks

Power Consumption (Max TDP)

GeForce GT 220 GDDR3		58 Watts
GeForce GT 640 DDR3		65 Watts
	Difference: 7 Watts (12%)

Memory Bandwidth

Theoretically, the GeForce GT 640 DDR3 should be quite a bit faster than the GeForce GT 220 GDDR3 in general. (explain)

GeForce GT 640 DDR3		57024 MB/sec
GeForce GT 220 GDDR3		32384 MB/sec
	Difference: 24640 (76%)

Texel Rate

The GeForce GT 640 DDR3 is much (approximately 188%) faster with regards to AF than the GeForce GT 220 GDDR3. (explain)

GeForce GT 640 DDR3		28800 Mtexels/sec
GeForce GT 220 GDDR3		10000 Mtexels/sec
	Difference: 18800 (188%)

Pixel Rate

If using high levels of AA is important to you, then the GeForce GT 640 DDR3 is the winner, by a large margin. (explain)

GeForce GT 640 DDR3		14400 Mpixels/sec
GeForce GT 220 GDDR3		5000 Mpixels/sec
	Difference: 9400 (188%)

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.

Price Comparison

Specifications

Memory Bandwidth: Bandwidth is the largest amount of information (in units of MB per second) that can be transferred past the external memory interface in one second. It's calculated by multiplying the interface width by its memory clock speed. If it uses DDR type memory, the result should be multiplied by 2 again. If DDR5, multiply by 4 instead. The better the memory bandwidth, the better the card will be in general. It especially helps with AA, HDR and higher screen resolutions.

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

Pixel Rate: Pixel rate is the most pixels the video card can 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 core speed of the card. ROPs (Raster Operations Pipelines - aka Render Output Units) are responsible for outputting the pixels (image) to the screen. The actual pixel rate is also dependant on quite a few other factors, especially the memory bandwidth - the lower the bandwidth is, the lower the potential to reach the maximum fill rate.