GeForce GT 640 DDR3 vs Radeon HD 4790

Intro

Compare all of that to the Radeon HD 4790, which makes use of a 55 nm design. AMD has clocked the core frequency at 600 MHz. The GDDR5 RAM runs at a speed of 800 MHz on this model. It features 640(128x5) SPUs as well as 32 Texture Address Units and 16 Rasterization Operator Units.

Display Graphs

Hide Graphs

Power Usage and Theoretical Benchmarks

Memory Bandwidth

The Radeon HD 4790 should in theory perform quite a bit faster than the GeForce GT 640 DDR3 overall. (explain)

Radeon HD 4790		102400 MB/sec
GeForce GT 640 DDR3		57024 MB/sec
	Difference: 45376 (80%)

Texel Rate

The GeForce GT 640 DDR3 will be a lot (more or less 50%) better at texture filtering than the Radeon HD 4790. (explain)

GeForce GT 640 DDR3		28800 Mtexels/sec
Radeon HD 4790		19200 Mtexels/sec
	Difference: 9600 (50%)

Pixel Rate

The GeForce GT 640 DDR3 will be a lot (about 50%) more effective at FSAA than the Radeon HD 4790, and will be able to handle higher screen resolutions without losing too much performance. (explain)

GeForce GT 640 DDR3		14400 Mpixels/sec
Radeon HD 4790		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 largest amount of data (in units of megabytes per second) that can be moved past the external memory interface in a second. It's calculated by multiplying the card's interface width by the speed of its memory. In the case of DDR RAM, it should be multiplied by 2 once again. If it uses DDR5, multiply by ANOTHER 2x. The higher the memory bandwidth, the better the card will be in general. It especially helps with anti-aliasing, HDR and high resolutions.

Texel Rate: Texel rate is the maximum amount of texture map elements (texels) that are processed in one second. This number is calculated by multiplying the total texture units of the card by the core clock speed of the chip. The better this number, the better the video 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 most pixels the video card could possibly write to its local memory per second - measured in millions of pixels per second. The number is calculated by multiplying the amount of ROPs 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 fill rate also depends on lots of other factors, most notably the memory bandwidth - the lower the memory bandwidth is, the lower the ability to get to the max fill rate.