Radeon HD 3870 1GB vs Radeon HD 4850 512MB

Intro

Compare those specifications to the Radeon HD 4850 512MB, which has core speeds of 625 MHz on the GPU, and 993 MHz on the 512 MB of GDDR3 RAM. It features 800(160x5) SPUs along with 40 Texture Address Units and 16 Rasterization Operator Units.

Display Graphs

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Power Usage and Theoretical Benchmarks

Power Consumption (Max TDP)

Radeon HD 3870 1GB		106 Watts
Radeon HD 4850 512MB		110 Watts
	Difference: 4 Watts (4%)

Memory Bandwidth

In theory, the Radeon HD 3870 1GB will be 13% faster than the Radeon HD 4850 512MB overall, because of its greater data rate. (explain)

Radeon HD 3870 1GB		72000 MB/sec
Radeon HD 4850 512MB		63552 MB/sec
	Difference: 8448 (13%)

Texel Rate

The Radeon HD 4850 512MB will be much (more or less 102%) more effective at AF than the Radeon HD 3870 1GB. (explain)

Radeon HD 4850 512MB		25000 Mtexels/sec
Radeon HD 3870 1GB		12400 Mtexels/sec
	Difference: 12600 (102%)

Pixel Rate

The Radeon HD 3870 1GB is a lot (approximately 24%) more effective at AA than the Radeon HD 4850 512MB, and also should be capable of handling higher screen resolutions without losing too much performance. (explain)

Radeon HD 3870 1GB		12400 Mpixels/sec
Radeon HD 4850 512MB		10000 Mpixels/sec
	Difference: 2400 (24%)

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 megabytes per second) that can be moved across the external memory interface within a second. The number is calculated by multiplying the card's bus width by the speed of its memory. If it uses DDR RAM, it must be multiplied by 2 again. If DDR5, multiply by 4 instead. The higher the card's memory bandwidth, the faster the card will be in general. It especially helps with AA, High Dynamic Range and higher screen resolutions.

Texel Rate: Texel rate is the maximum number of texture map elements (texels) that can be applied per second. This is worked out by multiplying the total texture units by the core speed of the chip. The higher this number, the better the video 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 maximum amount of pixels the video card can possibly write to its local memory in a second - measured in millions of pixels per second. Pixel rate is worked out by multiplying the number of ROPs by the clock speed of the card. ROPs (Raster Operations Pipelines - sometimes also referred to as Render Output Units) are responsible for filling the screen with pixels (the image). The actual pixel output rate is also dependant on many other factors, most notably the memory bandwidth - the lower the memory bandwidth is, the lower the potential to reach the max fill rate.