GeForce GT 640 DDR3 vs GeForce GTS 150

Intro

Compare that to the GeForce GTS 150, which has GPU clock speed of 740 MHz, and 1024 MB of GDDR3 memory set to run at 500 MHz through a 256-bit bus. It also is comprised of 128 SPUs, 64 Texture Address Units, and 16 ROPs.

Display Graphs

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Power Usage and Theoretical Benchmarks

Power Consumption (Max TDP)

GeForce GT 640 DDR3		65 Watts
GeForce GTS 150		141 Watts
	Difference: 76 Watts (117%)

Memory Bandwidth

Theoretically, the GeForce GT 640 DDR3 should be much faster than the GeForce GTS 150 in general. (explain)

GeForce GT 640 DDR3		57024 MB/sec
GeForce GTS 150		32000 MB/sec
	Difference: 25024 (78%)

Texel Rate

The GeForce GTS 150 is a lot (about 64%) better at AF than the GeForce GT 640 DDR3. (explain)

GeForce GTS 150		47360 Mtexels/sec
GeForce GT 640 DDR3		28800 Mtexels/sec
	Difference: 18560 (64%)

Pixel Rate

The GeForce GT 640 DDR3 should be much (more or less 22%) better at FSAA than the GeForce GTS 150, and also capable of handling higher resolutions without slowing down too much. (explain)

GeForce GT 640 DDR3		14400 Mpixels/sec
GeForce GTS 150		11840 Mpixels/sec
	Difference: 2560 (22%)

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: Memory bandwidth is the maximum amount of information (in units of MB per second) that can be transported over the external memory interface in a second. It is worked out by multiplying the card's interface width by the speed of its memory. In the case of DDR type RAM, the result should be multiplied by 2 once again. If DDR5, multiply by ANOTHER 2x. The better the memory bandwidth, the faster the card will be in general. It especially helps with AA, High Dynamic Range and higher screen resolutions.

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

Pixel Rate: Pixel rate is the most pixels that the graphics chip could possibly write to its local memory in one second - measured in millions of pixels per second. The figure is worked out by multiplying the number of ROPs by the the core clock speed. ROPs (Raster Operations Pipelines - also sometimes called Render Output Units) are responsible for outputting the pixels (image) to the screen. The actual pixel output rate also depends on quite a few other factors, most notably the memory bandwidth of the card - the lower the bandwidth is, the lower the potential to reach the maximum fill rate.