GeForce GT 640 DDR3 vs Radeon HD 4830 1GB

Intro

Compare all that to the Radeon HD 4830 1GB, which uses a 55 nm design. AMD has set the core frequency at 575 MHz. The GDDR4 memory works at a frequency of 900 MHz on this specific card. It features 640(128x5) SPUs as well as 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

Theoretically speaking, the Radeon HD 4830 1GB should be 1% quicker than the GeForce GT 640 DDR3 overall, because of its greater data rate. (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 should be a lot (approximately 57%) more effective 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 a lot (more or less 57%) faster with regards to anti-aliasing than the Radeon HD 4830 1GB, and also will be able to handle higher resolutions without slowing down too much. (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 (counted in MB per second) that can be transported across the external memory interface within a second. It's calculated by multiplying the interface width by its memory speed. If it uses DDR memory, the result should be multiplied by 2 once again. If DDR5, multiply by ANOTHER 2x. The higher the bandwidth is, the better 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 can be processed in one second. This figure is calculated by multiplying the total texture units by the core clock speed of the chip. The better this number, the better the graphics 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 maximum number of pixels that the graphics card can possibly write to its local memory in a second - measured in millions of pixels per second. The number is worked out by multiplying the amount of Render Output Units by the the card's clock speed. ROPs (Raster Operations Pipelines - also sometimes called Render Output Units) are responsible for outputting the pixels (image) to the screen. The actual pixel output rate is also dependant on many other factors, most notably the memory bandwidth of the card - the lower the bandwidth is, the lower the ability to reach the max fill rate.