GeForce 9400 GT 256MB vs GeForce GT 640 DDR3

Intro

Compare all of that to the GeForce GT 640 DDR3, which uses a 28 nm design. nVidia has set the core speed at 900 MHz. The DDR3 memory works at a speed of 1782 MHz on this particular card. 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 9400 GT 256MB		50 Watts
GeForce GT 640 DDR3		65 Watts
	Difference: 15 Watts (30%)

Memory Bandwidth

In theory, the GeForce GT 640 DDR3 is 346% faster than the GeForce 9400 GT 256MB in general, due to its higher bandwidth. (explain)

GeForce GT 640 DDR3		57024 MB/sec
GeForce 9400 GT 256MB		12800 MB/sec
	Difference: 44224 (346%)

Texel Rate

The GeForce GT 640 DDR3 will be quite a bit (more or less 555%) better at anisotropic filtering than the GeForce 9400 GT 256MB. (explain)

GeForce GT 640 DDR3		28800 Mtexels/sec
GeForce 9400 GT 256MB		4400 Mtexels/sec
	Difference: 24400 (555%)

Pixel Rate

If running with high levels of AA is important to you, then the GeForce GT 640 DDR3 is a better choice, by a large margin. (explain)

GeForce GT 640 DDR3		14400 Mpixels/sec
GeForce 9400 GT 256MB		2200 Mpixels/sec
	Difference: 12200 (555%)

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 MB per second) that can be transferred across the external memory interface in one second. It's worked out by multiplying the card's bus width by its memory speed. If the card has DDR type RAM, the result should be multiplied by 2 again. If it uses DDR5, multiply by ANOTHER 2x. The better the memory bandwidth, the faster 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 number of texture map elements (texels) that can be applied in one second. This is calculated by multiplying the total texture units 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 in a second.

Pixel Rate: Pixel rate is the maximum number of pixels the graphics card could possibly write to its local memory per second - measured in millions of pixels per second. Pixel rate is calculated by multiplying the amount of Raster Operations Pipelines by the clock 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 fill rate also depends on many other factors, most notably the memory bandwidth - the lower the bandwidth is, the lower the potential to reach the maximum fill rate.