GeForce GT 640 DDR3 vs Radeon HD 3850 256MB

Intro

Compare those specs to the Radeon HD 3850 256MB, which has a clock speed of 668 MHz and a GDDR3 memory speed of 828 MHz. It also uses a 256-bit memory bus, and makes use of a 55 nm design. It features 320(64x5) SPUs, 16 Texture Address Units, 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 3850 256MB		75 Watts
	Difference: 10 Watts (15%)

Memory Bandwidth

Theoretically speaking, the GeForce GT 640 DDR3 will be 8% quicker than the Radeon HD 3850 256MB in general, because of its greater bandwidth. (explain)

GeForce GT 640 DDR3		57024 MB/sec
Radeon HD 3850 256MB		52992 MB/sec
	Difference: 4032 (8%)

Texel Rate

The GeForce GT 640 DDR3 is quite a bit (approximately 169%) better at AF than the Radeon HD 3850 256MB. (explain)

GeForce GT 640 DDR3		28800 Mtexels/sec
Radeon HD 3850 256MB		10688 Mtexels/sec
	Difference: 18112 (169%)

Pixel Rate

The GeForce GT 640 DDR3 will be much (more or less 35%) faster with regards to full screen anti-aliasing than the Radeon HD 3850 256MB, and able to handle higher resolutions without losing too much performance. (explain)

GeForce GT 640 DDR3		14400 Mpixels/sec
Radeon HD 3850 256MB		10688 Mpixels/sec
	Difference: 3712 (35%)

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: Bandwidth is the max amount of data (measured in MB per second) that can be transported past the external memory interface in one second. It is worked out by multiplying the card's bus width by its memory speed. If the card has DDR RAM, it must be multiplied by 2 once again. If it uses DDR5, multiply by 4 instead. The higher the memory bandwidth, the better the card will be in general. It especially helps with anti-aliasing, High Dynamic Range and higher screen resolutions.

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

Pixel Rate: Pixel rate is the maximum number of pixels the video card can possibly write to the local memory in one second - measured in millions of pixels per second. The figure is worked out by multiplying the amount of Render Output Units by the the card's clock speed. 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 quite a few other factors, especially the memory bandwidth - the lower the memory bandwidth is, the lower the potential to get to the max fill rate.