GeForce GT 640 DDR3 vs Radeon HD 4770

Intro

Compare that to the Radeon HD 4770, which features a core clock speed of 750 MHz and a GDDR5 memory speed of 800 MHz. It also features a 128-bit bus, and makes use of a 40 nm design. It is comprised of 640(128x5) 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
Radeon HD 4770		80 Watts
	Difference: 15 Watts (23%)

Memory Bandwidth

In theory, the GeForce GT 640 DDR3 should be 11% quicker than the Radeon HD 4770 in general, because of its greater bandwidth. (explain)

GeForce GT 640 DDR3		57024 MB/sec
Radeon HD 4770		51200 MB/sec
	Difference: 5824 (11%)

Texel Rate

The GeForce GT 640 DDR3 is a small bit (approximately 20%) more effective at texture filtering than the Radeon HD 4770. (explain)

GeForce GT 640 DDR3		28800 Mtexels/sec
Radeon HD 4770		24000 Mtexels/sec
	Difference: 4800 (20%)

Pixel Rate

The GeForce GT 640 DDR3 should be a bit (more or less 20%) better at AA than the Radeon HD 4770, and will be capable of handling higher resolutions while still performing well. (explain)

GeForce GT 640 DDR3		14400 Mpixels/sec
Radeon HD 4770		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 max amount of information (in units of MB per second) that can be transported across the external memory interface in a second. It is calculated by multiplying the card's interface width by its memory clock speed. If it uses DDR memory, the result should be multiplied by 2 once again. If it uses DDR5, multiply by ANOTHER 2x. The higher the memory bandwidth, the faster the card will be in general. It especially helps with AA, High Dynamic Range and high resolutions.

Texel Rate: Texel rate is the maximum texture map elements (texels) that are applied in one 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 better this number, the better the card will be at handling texture filtering (anisotropic filtering - AF). It is measured in millions of texels applied in a second.

Pixel Rate: Pixel rate is the most pixels that the graphics chip 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 Raster Operations Pipelines by the the core 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 output rate also depends on many other factors, especially the memory bandwidth of the card - the lower the memory bandwidth is, the lower the ability to get to the maximum fill rate.