Radeon HD 4870 512MB vs Radeon HD 6750

Intro

Compare those specifications to the Radeon HD 6750, which has a clock speed of 725 MHz and a GDDR5 memory speed of 1000 MHz. It also uses a 128-bit memory bus, and makes use of a 40 nm design. It is made up of 720 SPUs, 36 TAUs, and 16 Raster Operation Units.

Display Graphs

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Power Usage and Theoretical Benchmarks

Power Consumption (Max TDP)

Radeon HD 6750		86 Watts
Radeon HD 4870 512MB		150 Watts
	Difference: 64 Watts (74%)

Memory Bandwidth

In theory, the Radeon HD 4870 512MB should be 80% faster than the Radeon HD 6750 overall, due to its higher data rate. (explain)

Radeon HD 4870 512MB		115200 MB/sec
Radeon HD 6750		64000 MB/sec
	Difference: 51200 (80%)

Texel Rate

The Radeon HD 4870 512MB will be just a bit (more or less 15%) more effective at texture filtering than the Radeon HD 6750. (explain)

Radeon HD 4870 512MB		30000 Mtexels/sec
Radeon HD 6750		26100 Mtexels/sec
	Difference: 3900 (15%)

Pixel Rate

If using a high resolution is important to you, then the Radeon HD 4870 512MB is superior to the Radeon HD 6750, though not by far. (explain)

Radeon HD 4870 512MB		12000 Mpixels/sec
Radeon HD 6750		11600 Mpixels/sec
	Difference: 400 (3%)

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 (measured in megabytes per second) that can be moved across the external memory interface in one second. The number is worked out by multiplying the card's interface width by its memory speed. If the card has DDR memory, it should be multiplied by 2 again. If it uses DDR5, multiply by 4 instead. The better the card's memory bandwidth, the better the card will be in general. It especially helps with AA, HDR 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 number of texture units by the core speed of the chip. The better this number, the better the 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 maximum amount of pixels that the graphics chip can possibly record to its local memory in a second - measured in millions of pixels per second. Pixel rate is worked out by multiplying the number of Raster Operations Pipelines by the the card's clock speed. ROPs (Raster Operations Pipelines - also called Render Output Units) are responsible for outputting the pixels (image) to the screen. The actual pixel rate also depends on many other factors, most notably the memory bandwidth of the card - the lower the bandwidth is, the lower the potential to reach the maximum fill rate.