GeForce 8800 GT 256MB vs GeForce GT 640 DDR3

Intro

Compare all of that to the GeForce GT 640 DDR3, which comes with a core clock speed of 900 MHz and a DDR3 memory speed of 1782 MHz. It also makes use of a 128-bit memory bus, and makes use of a 28 nm design. It features 384 SPUs, 32 TAUs, and 16 Raster Operation Units.

Display Graphs

Hide Graphs

Power Usage and Theoretical Benchmarks

Power Consumption (Max TDP)

GeForce GT 640 DDR3		65 Watts
GeForce 8800 GT 256MB		105 Watts
	Difference: 40 Watts (62%)

Memory Bandwidth

The GeForce GT 640 DDR3, in theory, should be much faster than the GeForce 8800 GT 256MB in general. (explain)

GeForce GT 640 DDR3		57024 MB/sec
GeForce 8800 GT 256MB		44800 MB/sec
	Difference: 12224 (27%)

Texel Rate

The GeForce 8800 GT 256MB is just a bit (about 17%) more effective at texture filtering than the GeForce GT 640 DDR3. (explain)

GeForce 8800 GT 256MB		33600 Mtexels/sec
GeForce GT 640 DDR3		28800 Mtexels/sec
	Difference: 4800 (17%)

Pixel Rate

The GeForce GT 640 DDR3 should be quite a bit (about 50%) better at FSAA than the GeForce 8800 GT 256MB, and also will be able to handle higher screen resolutions while still performing well. (explain)

GeForce GT 640 DDR3		14400 Mpixels/sec
GeForce 8800 GT 256MB		9600 Mpixels/sec
	Difference: 4800 (50%)

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 (measured in MB per second) that can be transported across the external memory interface within a second. The number is calculated by multiplying the card's interface width by the speed of its memory. If it uses DDR memory, the result should be multiplied by 2 once again. If it uses DDR5, multiply by 4 instead. The higher the bandwidth is, 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 processed per second. This figure is worked out by multiplying the total number of texture units of the card by the core clock 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 per second.

Pixel Rate: Pixel rate is the most pixels the graphics card can possibly write to its local memory in a second - measured in millions of pixels per second. Pixel rate is calculated by multiplying the amount of Raster Operations Pipelines by the the core speed of the card. ROPs (Raster Operations Pipelines - also sometimes called Render Output Units) are responsible for drawing the pixels (image) on the screen. The actual pixel rate is also dependant on quite a few other factors, most notably the memory bandwidth - the lower the bandwidth is, the lower the potential to reach the max fill rate.