GeForce GT 640 DDR3 vs Radeon HD 4830 1GB

Intro

Compare those specs to the Radeon HD 4830 1GB, which features a core clock frequency of 575 MHz and a GDDR4 memory frequency 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 Texture Address Units, and 16 Raster Operation 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 1GB		95 Watts
	Difference: 30 Watts (46%)

Memory Bandwidth

As far as performance goes, the Radeon HD 4830 1GB should in theory be just a bit superior to the GeForce GT 640 DDR3 overall. (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%) faster with regards to 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 is much (approximately 57%) more effective at full screen anti-aliasing than the Radeon HD 4830 1GB, and also will be able to handle higher screen resolutions more effectively. (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 largest amount of data (counted in megabytes per second) that can be transferred across the external memory interface in one second. It is worked out by multiplying the card's bus width by the speed of its memory. In the case of DDR type memory, it should be multiplied by 2 again. If it uses DDR5, multiply by 4 instead. The higher the memory bandwidth, the faster the card will be in general. It especially helps with AA, High Dynamic Range and high resolutions.

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

Pixel Rate: Pixel rate is the maximum amount of pixels the video card can possibly record to its local memory in one second - measured in millions of pixels per second. The number is calculated by multiplying the number 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 rate is also dependant on many other factors, especially the memory bandwidth of the card - the lower the bandwidth is, the lower the potential to reach the maximum fill rate.