GeForce GT 640 DDR3 vs Radeon HD 4870 1GB

Intro

Compare all of that to the Radeon HD 4870 1GB, which has core clock speeds of 750 MHz on the GPU, and 900 MHz on the 1024 MB of GDDR5 RAM. It features 800(160x5) SPUs along with 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

The Radeon HD 4870 1GB, in theory, should perform a lot faster than the GeForce GT 640 DDR3 overall. (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 will be a little bit (approximately 4%) faster with regards to anisotropic 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 is a bit (about 20%) faster with regards to anti-aliasing than the Radeon HD 4870 1GB, and also will be capable of handling higher resolutions without losing too much performance. (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 (counted in MB per second) that can be transported over the external memory interface in a second. It is worked out by multiplying the bus width by its memory clock speed. In the case of DDR RAM, the result should be multiplied by 2 once again. If DDR5, multiply by 4 instead. The higher the card's memory bandwidth, the faster 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 amount of texture map elements (texels) that can be processed per second. This number is calculated by multiplying the total amount of texture units of the card by the core speed of the chip. The better this number, the better the video 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 per second - measured in millions of pixels per second. Pixel rate is calculated by multiplying the number of colour ROPs by the clock speed of the card. ROPs (Raster Operations Pipelines - also sometimes called Render Output Units) are responsible for filling the screen with pixels (the image). The actual pixel rate is also dependant on quite a few other factors, especially the memory bandwidth - the lower the memory bandwidth is, the lower the ability to reach the max fill rate.