GeForce GT 640 DDR3 vs GeForce GTS 150

Intro

Compare those specs to the GeForce GTS 150, which uses a 55 nm design. nVidia has set the core frequency at 740 MHz. The GDDR3 memory works at a frequency of 500 MHz on this specific card. It features 128 SPUs along with 64 TAUs 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

Performance-wise, the GeForce GT 640 DDR3 should in theory be much superior to the GeForce GTS 150 overall. (explain)

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

Texel Rate

The GeForce GTS 150 will be quite a bit (approximately 64%) more effective at texture filtering 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 will be quite a bit (approximately 22%) faster with regards to full screen anti-aliasing than the GeForce GTS 150, and will be 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: Bandwidth is the max amount of data (in units of megabytes per second) that can be moved across the external memory interface within a second. It is worked out by multiplying the bus width by its memory clock speed. If the card has DDR memory, the result should be multiplied by 2 again. If it uses DDR5, multiply by ANOTHER 2x. The higher the bandwidth is, the faster the card will be in general. It especially helps with anti-aliasing, HDR and high resolutions.

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

Pixel Rate: Pixel rate is the most pixels that the graphics chip can possibly write to the local memory per second - measured in millions of pixels per second. Pixel rate is worked out by multiplying the amount of ROPs by the the core speed of the card. ROPs (Raster Operations Pipelines - aka Render Output Units) are responsible for filling the screen with pixels (the image). The actual pixel rate also depends on many 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.