GeForce GT 640 DDR3 vs Radeon HD 4890 1GB

Intro

Compare those specifications to the Radeon HD 4890 1GB, which has a clock speed of 1000 MHz and a GDDR5 memory frequency of 975 MHz. It also uses a 256-bit bus, and uses a 55 nm design. It is made up of 800(160x5) SPUs, 40 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 4890 1GB		190 Watts
	Difference: 125 Watts (192%)

Memory Bandwidth

Performance-wise, the Radeon HD 4890 1GB should theoretically be much superior to the GeForce GT 640 DDR3 in general. (explain)

Radeon HD 4890 1GB		124800 MB/sec
GeForce GT 640 DDR3		57024 MB/sec
	Difference: 67776 (119%)

Texel Rate

The Radeon HD 4890 1GB is a lot (about 39%) more effective at texture filtering than the GeForce GT 640 DDR3. (explain)

Radeon HD 4890 1GB		40000 Mtexels/sec
GeForce GT 640 DDR3		28800 Mtexels/sec
	Difference: 11200 (39%)

Pixel Rate

If using lots of anti-aliasing is important to you, then the Radeon HD 4890 1GB is superior to the GeForce GT 640 DDR3, though not by far. (explain)

Radeon HD 4890 1GB		16000 Mpixels/sec
GeForce GT 640 DDR3		14400 Mpixels/sec
	Difference: 1600 (11%)

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 max amount of data (measured in megabytes per second) that can be transported over the external memory interface in a second. It is calculated by multiplying the bus width by the speed of its memory. In the case of DDR memory, the result should be multiplied by 2 again. If DDR5, multiply by ANOTHER 2x. The higher the memory bandwidth, 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 can be applied per second. This is worked out by multiplying the total texture units of the card by the core speed of the chip. The higher this number, the better the card will be at texture filtering (anisotropic filtering - AF). It is measured in millions of texels processed in one second.

Pixel Rate: Pixel rate is the most pixels that the graphics card could possibly record to the local memory in one second - measured in millions of pixels per second. The number is worked out by multiplying the amount of ROPs by the clock speed of the card. 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 rate is also dependant on many other factors, especially the memory bandwidth - the lower the memory bandwidth is, the lower the ability to get to the max fill rate.