GeForce GT 640 DDR3 vs Radeon HD 4830 512MB

Intro

Compare all of that to the Radeon HD 4830 512MB, which has a GPU core clock speed of 575 MHz, and 512 MB of GDDR3 memory running at 900 MHz through a 256-bit bus. It also is comprised of 640(128x5) Stream Processors, 32 Texture Address Units, and 16 ROPs.

Display Graphs

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Power Usage and Theoretical Benchmarks

Power Consumption (Max TDP)

GeForce GT 640 DDR3		65 Watts
Radeon HD 4830 512MB		95 Watts
	Difference: 30 Watts (46%)

Memory Bandwidth

In theory, the Radeon HD 4830 512MB will be 1% faster than the GeForce GT 640 DDR3 overall, due to its higher bandwidth. (explain)

Radeon HD 4830 512MB		57600 MB/sec
GeForce GT 640 DDR3		57024 MB/sec
	Difference: 576 (1%)

Texel Rate

The GeForce GT 640 DDR3 should be quite a bit (more or less 57%) better at AF than the Radeon HD 4830 512MB. (explain)

GeForce GT 640 DDR3		28800 Mtexels/sec
Radeon HD 4830 512MB		18400 Mtexels/sec
	Difference: 10400 (57%)

Pixel Rate

The GeForce GT 640 DDR3 is quite a bit (more or less 57%) better at full screen anti-aliasing than the Radeon HD 4830 512MB, and will be capable of handling higher screen resolutions better. (explain)

GeForce GT 640 DDR3		14400 Mpixels/sec
Radeon HD 4830 512MB		9200 Mpixels/sec
	Difference: 5200 (57%)

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 maximum amount of information (measured in megabytes per second) that can be transported across the external memory interface in one second. It is worked out by multiplying the card's interface width by the speed of its memory. In the case of DDR memory, the result should be multiplied by 2 again. If it uses DDR5, multiply by ANOTHER 2x. The higher the card's memory bandwidth, the faster the card will be in general. It especially helps with anti-aliasing, HDR and higher screen resolutions.

Texel Rate: Texel rate is the maximum texture map elements (texels) that can be processed in one second. This is calculated by multiplying the total amount of texture units by the core clock speed of the chip. The better this number, the better the card will be at texture filtering (anisotropic filtering - AF). It is measured in millions of texels applied in one second.

Pixel Rate: Pixel rate is the most pixels the video 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 Render Output Units by the clock speed of the card. ROPs (Raster Operations Pipelines - sometimes also referred to as Render Output Units) are responsible for filling the screen with pixels (the image). The actual pixel fill rate is also dependant on many other factors, most notably the memory bandwidth - the lower the memory bandwidth is, the lower the potential to get to the maximum fill rate.