GeForce GT 640 DDR3 vs Radeon HD 4850 2GB

Intro

Compare those specs to the Radeon HD 4850 2GB, which uses a 55 nm design. AMD has set the core frequency at 625 MHz. The GDDR4 memory is set to run at a speed of 993 MHz on this specific card. It features 800(160x5) SPUs as well as 40 Texture Address Units and 16 Rasterization Operator Units.

Display Graphs

Hide Graphs

Power Usage and Theoretical Benchmarks

Power Consumption (Max TDP)

GeForce GT 640 DDR3		65 Watts
Radeon HD 4850 2GB		110 Watts
	Difference: 45 Watts (69%)

Memory Bandwidth

Performance-wise, the Radeon HD 4850 2GB should in theory be a small bit superior to the GeForce GT 640 DDR3 overall. (explain)

Radeon HD 4850 2GB		63552 MB/sec
GeForce GT 640 DDR3		57024 MB/sec
	Difference: 6528 (11%)

Texel Rate

The GeForce GT 640 DDR3 will be just a bit (more or less 15%) more effective at AF than the Radeon HD 4850 2GB. (explain)

GeForce GT 640 DDR3		28800 Mtexels/sec
Radeon HD 4850 2GB		25000 Mtexels/sec
	Difference: 3800 (15%)

Pixel Rate

The GeForce GT 640 DDR3 is quite a bit (more or less 44%) faster with regards to anti-aliasing than the Radeon HD 4850 2GB, and also will be capable of handling higher resolutions better. (explain)

GeForce GT 640 DDR3		14400 Mpixels/sec
Radeon HD 4850 2GB		10000 Mpixels/sec
	Difference: 4400 (44%)

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 (in units of MB per second) that can be transferred over the external memory interface in a second. It is calculated by multiplying the card's interface width by its memory speed. In the case of DDR memory, the result should be multiplied by 2 once again. If DDR5, multiply by ANOTHER 2x. The higher the card's 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 amount of texture map elements (texels) that are processed per second. This number is worked out by multiplying the total number of texture units by the core clock speed of the chip. The better the texel rate, the better the video card will be at handling texture filtering (anisotropic filtering - AF). It is measured in millions of texels processed in one second.

Pixel Rate: Pixel rate is the most pixels the graphics card could possibly write to the local memory in one second - measured in millions of pixels per second. Pixel rate is calculated by multiplying the amount of ROPs by the the core speed of the card. ROPs (Raster Operations Pipelines - aka Render Output Units) are responsible for filling the screen with pixels (the image). The actual pixel fill rate also depends on many other factors, most notably the memory bandwidth of the card - the lower the bandwidth is, the lower the ability to get to the maximum fill rate.