GeForce GT 640 DDR3 vs Radeon HD 4830 1GB

Intro

Compare all of that to the Radeon HD 4830 1GB, which features a core clock speed of 575 MHz and a GDDR4 memory speed of 900 MHz. It also uses a 256-bit memory bus, and makes use of a 55 nm design. It is comprised of 640(128x5) SPUs, 32 TAUs, 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 1GB		95 Watts
	Difference: 30 Watts (46%)

Memory Bandwidth

Performance-wise, the Radeon HD 4830 1GB should theoretically be a small bit superior to the GeForce GT 640 DDR3 in general. (explain)

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

Texel Rate

The GeForce GT 640 DDR3 is a lot (about 57%) better at anisotropic filtering than the Radeon HD 4830 1GB. (explain)

GeForce GT 640 DDR3		28800 Mtexels/sec
Radeon HD 4830 1GB		18400 Mtexels/sec
	Difference: 10400 (57%)

Pixel Rate

The GeForce GT 640 DDR3 will be much (approximately 57%) more effective at full screen anti-aliasing than the Radeon HD 4830 1GB, and also capable of handling higher resolutions better. (explain)

GeForce GT 640 DDR3		14400 Mpixels/sec
Radeon HD 4830 1GB		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: Memory bandwidth is the maximum amount of information (in units of MB per second) that can be transported across the external memory interface in one second. It is calculated by multiplying the card's bus width by its memory speed. If it uses DDR type RAM, it must be multiplied by 2 once again. If DDR5, multiply by ANOTHER 2x. The better the bandwidth is, the faster the card will be in general. It especially helps with AA, HDR and higher screen resolutions.

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

Pixel Rate: Pixel rate is the maximum amount of pixels the graphics card can possibly record to the local memory in one second - measured in millions of pixels per second. The figure is worked out by multiplying the number of Render Output Units by the the core 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 rate is also dependant on many other factors, especially the memory bandwidth of the card - the lower the bandwidth is, the lower the ability to reach the maximum fill rate.