GeForce 8400 GS 512MB vs GeForce GT 640 DDR3

Intro

Compare all of that to the GeForce GT 640 DDR3, which features core speeds of 900 MHz on the GPU, and 1782 MHz on the 2048 MB of DDR3 RAM. It features 384 SPUs as well as 32 Texture Address Units and 16 ROPs.

Display Graphs

Hide Graphs

Power Usage and Theoretical Benchmarks

Power Consumption (Max TDP)

GeForce 8400 GS 512MB		40 Watts
GeForce GT 640 DDR3		65 Watts
	Difference: 25 Watts (63%)

Memory Bandwidth

The GeForce GT 640 DDR3, in theory, should perform a lot faster than the GeForce 8400 GS 512MB in general. (explain)

GeForce GT 640 DDR3		57024 MB/sec
GeForce 8400 GS 512MB		6400 MB/sec
	Difference: 50624 (791%)

Texel Rate

The GeForce GT 640 DDR3 will be much (about 454%) more effective at anisotropic filtering than the GeForce 8400 GS 512MB. (explain)

GeForce GT 640 DDR3		28800 Mtexels/sec
GeForce 8400 GS 512MB		5200 Mtexels/sec
	Difference: 23600 (454%)

Pixel Rate

The GeForce GT 640 DDR3 is a lot (about 454%) more effective at AA than the GeForce 8400 GS 512MB, and also able to handle higher resolutions without losing too much performance. (explain)

GeForce GT 640 DDR3		14400 Mpixels/sec
GeForce 8400 GS 512MB		2600 Mpixels/sec
	Difference: 11800 (454%)

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 over the external memory interface in one second. The number is worked out by multiplying the interface width by the speed of its memory. If the card has DDR type RAM, it must be multiplied by 2 once again. If it uses DDR5, multiply by ANOTHER 2x. The better the card's memory bandwidth, the better the card will be in general. It especially helps with AA, High Dynamic Range and high resolutions.

Texel Rate: Texel rate is the maximum texture map elements (texels) that are processed in one second. This figure is calculated by multiplying the total number of 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 per second.

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