GeForce 8800 GT 1GB vs GeForce GT 640 DDR3

Intro

Compare that to the GeForce GT 640 DDR3, which comes with GPU clock speed of 900 MHz, and 2048 MB of DDR3 memory set to run at 1782 MHz through a 128-bit bus. It also is made up of 384 SPUs, 32 TAUs, and 16 ROPs.

Display Graphs

Hide Graphs

Power Usage and Theoretical Benchmarks

Power Consumption (Max TDP)

GeForce GT 640 DDR3		65 Watts
GeForce 8800 GT 1GB		105 Watts
	Difference: 40 Watts (62%)

Memory Bandwidth

As far as performance goes, the GeForce 8800 GT 1GB should in theory be a little bit superior to the GeForce GT 640 DDR3 overall. (explain)

GeForce 8800 GT 1GB		57600 MB/sec
GeForce GT 640 DDR3		57024 MB/sec
	Difference: 576 (1%)

Texel Rate

The GeForce 8800 GT 1GB is just a bit (more or less 17%) more effective at anisotropic filtering than the GeForce GT 640 DDR3. (explain)

GeForce 8800 GT 1GB		33600 Mtexels/sec
GeForce GT 640 DDR3		28800 Mtexels/sec
	Difference: 4800 (17%)

Pixel Rate

The GeForce GT 640 DDR3 is quite a bit (approximately 50%) more effective at anti-aliasing than the GeForce 8800 GT 1GB, and also will be capable of handling higher resolutions more effectively. (explain)

GeForce GT 640 DDR3		14400 Mpixels/sec
GeForce 8800 GT 1GB		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: Memory bandwidth is the maximum amount of data (measured in megabytes per second) that can be moved across the external memory interface within a second. It is worked out by multiplying the bus width by the speed of its memory. In the case of DDR RAM, the result should be multiplied by 2 once again. If DDR5, multiply by ANOTHER 2x. The higher the bandwidth is, the better the card will be in general. It especially helps with anti-aliasing, High Dynamic Range and high resolutions.

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

Pixel Rate: Pixel rate is the maximum number of pixels the graphics card could possibly record to its local memory in one 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 outputting the pixels (image) to the screen. The actual pixel rate also depends on quite a few other factors, most notably the memory bandwidth of the card - the lower the memory bandwidth is, the lower the potential to get to the maximum fill rate.