GeForce GT 640 DDR3 vs Radeon HD 4870 1GB

Intro

Compare those specifications to the Radeon HD 4870 1GB, which features clock speeds of 750 MHz on the GPU, and 900 MHz on the 1024 MB of GDDR5 RAM. It features 800(160x5) SPUs as well as 40 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
Radeon HD 4870 1GB		150 Watts
	Difference: 85 Watts (131%)

Memory Bandwidth

Theoretically speaking, the Radeon HD 4870 1GB will be 102% quicker than the GeForce GT 640 DDR3 in general, because of its greater data rate. (explain)

Radeon HD 4870 1GB		115200 MB/sec
GeForce GT 640 DDR3		57024 MB/sec
	Difference: 58176 (102%)

Texel Rate

The Radeon HD 4870 1GB should be just a bit (about 4%) more effective at texture filtering than the GeForce GT 640 DDR3. (explain)

Radeon HD 4870 1GB		30000 Mtexels/sec
GeForce GT 640 DDR3		28800 Mtexels/sec
	Difference: 1200 (4%)

Pixel Rate

The GeForce GT 640 DDR3 will be a small bit (approximately 20%) more effective at anti-aliasing than the Radeon HD 4870 1GB, and also should be capable of handling higher resolutions more effectively. (explain)

GeForce GT 640 DDR3		14400 Mpixels/sec
Radeon HD 4870 1GB		12000 Mpixels/sec
	Difference: 2400 (20%)

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 largest amount of information (in units of MB per second) that can be transferred over the external memory interface within a second. It's worked out by multiplying the card's interface width by its memory speed. In the case of DDR memory, it must be multiplied by 2 again. If it uses DDR5, multiply by 4 instead. The higher the memory bandwidth, the faster the card will be in general. It especially helps with AA, High Dynamic Range and higher screen resolutions.

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

Pixel Rate: Pixel rate is the maximum amount of pixels the graphics card could possibly write to the local memory in one second - measured in millions of pixels per second. The figure is worked out by multiplying the number of colour ROPs by the the core speed of the card. ROPs (Raster Operations Pipelines - also called Render Output Units) are responsible for drawing the pixels (image) on the screen. The actual pixel output rate also depends on many other factors, especially the memory bandwidth - the lower the bandwidth is, the lower the ability to get to the maximum fill rate.