GeForce 9800 GTX+ vs GeForce GT 640 DDR3

Intro

Compare those specs to the GeForce GT 640 DDR3, which features clock speeds of 900 MHz on the GPU, and 1782 MHz on the 2048 MB of DDR3 memory. It features 384 SPUs along with 32 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 9800 GTX+		145 Watts
	Difference: 80 Watts (123%)

Memory Bandwidth

Theoretically, the GeForce 9800 GTX+ should be quite a bit faster than the GeForce GT 640 DDR3 overall. (explain)

GeForce 9800 GTX+		70400 MB/sec
GeForce GT 640 DDR3		57024 MB/sec
	Difference: 13376 (23%)

Texel Rate

The GeForce 9800 GTX+ will be a lot (approximately 64%) faster with regards to AF than the GeForce GT 640 DDR3. (explain)

GeForce 9800 GTX+		47232 Mtexels/sec
GeForce GT 640 DDR3		28800 Mtexels/sec
	Difference: 18432 (64%)

Pixel Rate

The GeForce GT 640 DDR3 is much (about 22%) better at AA than the GeForce 9800 GTX+, and also able to handle higher screen resolutions more effectively. (explain)

GeForce GT 640 DDR3		14400 Mpixels/sec
GeForce 9800 GTX+		11808 Mpixels/sec
	Difference: 2592 (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 maximum amount of data (counted in MB per second) that can be transferred past the external memory interface in a second. The number is worked out by multiplying the interface width by its memory clock speed. If the card has DDR type memory, it must be multiplied by 2 again. If it uses DDR5, multiply by ANOTHER 2x. The higher the card's 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 can be processed in one second. This figure is worked out by multiplying the total amount of texture units by the core clock speed of the chip. The better this number, the better the video card will be at handling texture filtering (anisotropic filtering - AF). It is measured in millions of texels in one second.

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