GeForce GT 640 DDR3 vs Radeon HD 4830 512MB

Intro

Compare all that to the Radeon HD 4830 512MB, which uses a 55 nm design. AMD has clocked the core frequency at 575 MHz. The GDDR3 RAM runs at a speed of 900 MHz on this particular card. It features 640(128x5) SPUs along with 32 TAUs and 16 Rasterization Operator Units.

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 should be 1% quicker than the GeForce GT 640 DDR3 overall, due to its greater data rate. (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 (approximately 57%) more effective at texture filtering 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

If using a high resolution is important to you, then the GeForce GT 640 DDR3 is the winner, by far. (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: Memory bandwidth is the max amount of data (measured in megabytes per second) that can be transferred past the external memory interface within a second. The number is worked out by multiplying the card's interface width by its memory clock speed. If it uses DDR type memory, it must be multiplied by 2 once again. If DDR5, multiply by ANOTHER 2x. The better the memory bandwidth, the faster the card will be in general. It especially helps with anti-aliasing, High Dynamic Range and high resolutions.

Texel Rate: Texel rate is the maximum number of texture map elements (texels) that are applied in one second. This number is worked out by multiplying the total texture units of the card 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 in one second.

Pixel Rate: Pixel rate is the maximum amount of pixels that the graphics card can possibly record to its 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 the card's clock speed. ROPs (Raster Operations Pipelines - aka Render Output Units) are responsible for outputting the pixels (image) to the screen. The actual pixel rate is also dependant on quite a few other factors, most notably the memory bandwidth - the lower the bandwidth is, the lower the ability to get to the max fill rate.