GeForce GT 640 DDR3 vs Radeon HD 4870 2GB

Intro

Compare all of that to the Radeon HD 4870 2GB, which comes with a clock speed of 750 MHz and a GDDR5 memory speed of 900 MHz. It also uses a 256-bit bus, and uses a 55 nm design. It is comprised of 800(160x5) SPUs, 40 Texture Address Units, and 16 Raster Operation Units.

Display Graphs

Hide Graphs

Power Usage and Theoretical Benchmarks

Power Consumption (Max TDP)

GeForce GT 640 DDR3		65 Watts
Radeon HD 4870 2GB		150 Watts
	Difference: 85 Watts (131%)

Memory Bandwidth

The Radeon HD 4870 2GB should in theory be much faster than the GeForce GT 640 DDR3 in general. (explain)

Radeon HD 4870 2GB		115200 MB/sec
GeForce GT 640 DDR3		57024 MB/sec
	Difference: 58176 (102%)

Texel Rate

The Radeon HD 4870 2GB is a little bit (about 4%) better at anisotropic filtering than the GeForce GT 640 DDR3. (explain)

Radeon HD 4870 2GB		30000 Mtexels/sec
GeForce GT 640 DDR3		28800 Mtexels/sec
	Difference: 1200 (4%)

Pixel Rate

If running with a high resolution is important to you, then the GeForce GT 640 DDR3 is superior to the Radeon HD 4870 2GB, but only just. (explain)

GeForce GT 640 DDR3		14400 Mpixels/sec
Radeon HD 4870 2GB		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 data (counted in MB per second) that can be transported past the external memory interface within a second. It is worked out by multiplying the bus width by its memory clock speed. If the card has DDR memory, it must be multiplied by 2 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 amount of texture map elements (texels) that are processed per second. This is calculated by multiplying the total amount of texture units by the core clock speed of the chip. The better the texel rate, the better the card will be at texture filtering (anisotropic filtering - AF). It is measured in millions of texels processed in a second.

Pixel Rate: Pixel rate is the maximum amount of pixels the video card could possibly write to the local memory per second - measured in millions of pixels per second. Pixel rate is calculated by multiplying the amount of colour ROPs by the the card's clock speed. ROPs (Raster Operations Pipelines - sometimes also referred to as Render Output Units) are responsible for drawing the pixels (image) on the screen. The actual pixel fill rate is also dependant on quite a few other factors, especially the memory bandwidth - the lower the bandwidth is, the lower the potential to reach the maximum fill rate.