GeForce GTX 660 vs Radeon HD 4890 2GB

Intro

Compare those specifications to the Radeon HD 4890 2GB, which comes with a clock frequency of 1000 MHz and a GDDR5 memory speed of 975 MHz. It also makes use of a 256-bit bus, and makes use of a 55 nm design. It is made up of 800(160x5) SPUs, 40 Texture Address Units, and 16 Raster Operation Units.

Display Graphs

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Power Usage and Theoretical Benchmarks

Power Consumption (Max TDP)

GeForce GTX 660		140 Watts
Radeon HD 4890 2GB		190 Watts
	Difference: 50 Watts (36%)

Memory Bandwidth

Theoretically speaking, the GeForce GTX 660 should be 16% faster than the Radeon HD 4890 2GB in general, due to its greater data rate. (explain)

GeForce GTX 660		144192 MB/sec
Radeon HD 4890 2GB		124800 MB/sec
	Difference: 19392 (16%)

Texel Rate

The GeForce GTX 660 will be quite a bit (more or less 96%) faster with regards to AF than the Radeon HD 4890 2GB. (explain)

GeForce GTX 660		78400 Mtexels/sec
Radeon HD 4890 2GB		40000 Mtexels/sec
	Difference: 38400 (96%)

Pixel Rate

The GeForce GTX 660 should be quite a bit (about 47%) more effective at full screen anti-aliasing than the Radeon HD 4890 2GB, and will be capable of handling higher screen resolutions more effectively. (explain)

GeForce GTX 660		23520 Mpixels/sec
Radeon HD 4890 2GB		16000 Mpixels/sec
	Difference: 7520 (47%)

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 megabytes per second) that can be moved across the external memory interface within a second. The number is worked out by multiplying the card's interface width by its memory speed. If it uses DDR type RAM, the result should be multiplied by 2 again. If it uses DDR5, multiply by ANOTHER 2x. The better the bandwidth is, 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 number of texture map elements (texels) that are applied in one second. This number is calculated by multiplying the total number of texture units 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 maximum amount of pixels that the graphics chip can possibly write to its local memory in a second - measured in millions of pixels per second. Pixel rate is worked out by multiplying the amount of colour ROPs by the clock speed of the card. ROPs (Raster Operations Pipelines - also sometimes called Render Output Units) are responsible for outputting the pixels (image) to the screen. The actual pixel fill rate also depends on quite a few other factors, especially the memory bandwidth of the card - the lower the bandwidth is, the lower the ability to get to the maximum fill rate.