GeForce GT 640 DDR3 vs Radeon HD 4830 512MB

Intro

Compare those specs to the Radeon HD 4830 512MB, which uses a 55 nm design. AMD has clocked the core frequency at 575 MHz. The GDDR3 memory is set to run at a frequency of 900 MHz on this model. It features 640(128x5) SPUs along with 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 512MB		95 Watts
	Difference: 30 Watts (46%)

Memory Bandwidth

The Radeon HD 4830 512MB, in theory, should perform just a bit faster than the GeForce GT 640 DDR3 overall. (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 is a lot (about 57%) faster with regards to 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 should be much (about 57%) better at anti-aliasing than the Radeon HD 4830 512MB, and will be capable of handling higher screen resolutions while still performing well. (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 (in units of MB per second) that can be moved past the external memory interface within a second. It is calculated by multiplying the interface width by the speed of its memory. If the card has DDR memory, it must be multiplied by 2 again. If it uses DDR5, multiply by 4 instead. The better the card's memory bandwidth, the better 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 are applied in one second. This is worked out by multiplying the total texture units by the core clock speed of the chip. The better the texel rate, 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 most pixels the graphics card can possibly record to its local memory per second - measured in millions of pixels per second. The figure is calculated by multiplying the amount of ROPs by the the core speed of the card. ROPs (Raster Operations Pipelines - sometimes also referred to as Render Output Units) are responsible for outputting the pixels (image) to the screen. The actual pixel output rate also depends on many other factors, especially the memory bandwidth of the card - the lower the memory bandwidth is, the lower the ability to get to the maximum fill rate.