Radeon HD 3870 1GB vs Radeon HD 4650 1GB

Intro

Compare those specifications to the Radeon HD 4650 1GB, which features a core clock speed of 600 MHz and a GDDR3 memory frequency of 700 MHz. It also uses a 128-bit memory bus, and makes use of a 55 nm design. It features 320(64x5) SPUs, 32 Texture Address Units, and 8 Raster Operation Units.

Display Graphs

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Power Usage and Theoretical Benchmarks

Power Consumption (Max TDP)

Radeon HD 4650 1GB		55 Watts
Radeon HD 3870 1GB		106 Watts
	Difference: 51 Watts (93%)

Memory Bandwidth

Theoretically speaking, the Radeon HD 3870 1GB should be much faster than the Radeon HD 4650 1GB overall. (explain)

Radeon HD 3870 1GB		72000 MB/sec
Radeon HD 4650 1GB		22400 MB/sec
	Difference: 49600 (221%)

Texel Rate

The Radeon HD 4650 1GB should be much (about 55%) better at AF than the Radeon HD 3870 1GB. (explain)

Radeon HD 4650 1GB		19200 Mtexels/sec
Radeon HD 3870 1GB		12400 Mtexels/sec
	Difference: 6800 (55%)

Pixel Rate

If using high levels of AA is important to you, then the Radeon HD 3870 1GB is superior to the Radeon HD 4650 1GB, by a large margin. (explain)

Radeon HD 3870 1GB		12400 Mpixels/sec
Radeon HD 4650 1GB		4800 Mpixels/sec
	Difference: 7600 (158%)

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 information (counted in MB per second) that can be transferred across the external memory interface within a second. It's calculated by multiplying the interface width by its memory clock speed. If the card has DDR type memory, it must be multiplied by 2 again. If DDR5, multiply by 4 instead. The higher the bandwidth is, the better the card will be in general. It especially helps with AA, HDR and high resolutions.

Texel Rate: Texel rate is the maximum texture map elements (texels) that are processed per second. This figure is worked out by multiplying the total texture units of the card by the core speed of the chip. The higher this number, 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 could possibly record to the local memory in one second - measured in millions of pixels per second. Pixel rate is worked out by multiplying the number of ROPs by the the core 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 fill rate also depends on quite a few other factors, most notably the memory bandwidth - the lower the bandwidth is, the lower the potential to reach the max fill rate.