GeForce GT 640 DDR3 vs GeForce GTS 450 1GB

Intro

Compare those specifications to the GeForce GTS 450 1GB, which features a GPU core clock speed of 783 MHz, and 1024 MB of GDDR5 memory set to run at 902 MHz through a 128-bit bus. It also features 192 Stream Processors, 32 TAUs, and 16 Raster Operation Units.

Display Graphs

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Power Usage and Theoretical Benchmarks

Power Consumption (Max TDP)

GeForce GT 640 DDR3		65 Watts
GeForce GTS 450 1GB		106 Watts
	Difference: 41 Watts (63%)

Memory Bandwidth

In theory, the GeForce GTS 450 1GB is 1% quicker than the GeForce GT 640 DDR3 overall, because of its greater bandwidth. (explain)

GeForce GTS 450 1GB		57728 MB/sec
GeForce GT 640 DDR3		57024 MB/sec
	Difference: 704 (1%)

Texel Rate

The GeForce GT 640 DDR3 is a little bit (more or less 15%) faster with regards to texture filtering than the GeForce GTS 450 1GB. (explain)

GeForce GT 640 DDR3		28800 Mtexels/sec
GeForce GTS 450 1GB		25056 Mtexels/sec
	Difference: 3744 (15%)

Pixel Rate

If using lots of anti-aliasing is important to you, then the GeForce GT 640 DDR3 is superior to the GeForce GTS 450 1GB, though not by far. (explain)

GeForce GT 640 DDR3		14400 Mpixels/sec
GeForce GTS 450 1GB		12528 Mpixels/sec
	Difference: 1872 (15%)

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 maximum amount of information (measured in megabytes per second) that can be transported across the external memory interface within a second. The number is worked out by multiplying the interface width by its memory clock speed. If the card has DDR type RAM, it must be multiplied by 2 again. If DDR5, multiply by ANOTHER 2x. The better the memory bandwidth, the better the card will be in general. It especially helps with anti-aliasing, High Dynamic Range and higher screen resolutions.

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

Pixel Rate: Pixel rate is the most pixels the video card can possibly write to its local memory per second - measured in millions of pixels per second. The number is worked out by multiplying the number of ROPs by the the core clock speed. ROPs (Raster Operations Pipelines - also called Render Output Units) are responsible for filling the screen with pixels (the image). The actual pixel fill rate is also dependant on quite a few other factors, most notably the memory bandwidth - the lower the bandwidth is, the lower the ability to get to the max fill rate.