Radeon HD 4870 512MB vs Radeon HD 7850

Intro

Compare all of that to the Radeon HD 7850, which comes with a core clock frequency of 860 MHz and a GDDR5 memory frequency of 1200 MHz. It also uses a 256-bit bus, and makes use of a 28 nm design. It features 1024 SPUs, 64 TAUs, and 32 Raster Operation Units.

Display Graphs

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Power Usage and Theoretical Benchmarks

Power Consumption (Max TDP)

Radeon HD 7850		130 Watts
Radeon HD 4870 512MB		150 Watts
	Difference: 20 Watts (15%)

Memory Bandwidth

Theoretically speaking, the Radeon HD 7850 is 33% faster than the Radeon HD 4870 512MB overall, because of its higher data rate. (explain)

Radeon HD 7850		153600 MB/sec
Radeon HD 4870 512MB		115200 MB/sec
	Difference: 38400 (33%)

Texel Rate

The Radeon HD 7850 should be a lot (more or less 83%) faster with regards to AF than the Radeon HD 4870 512MB. (explain)

Radeon HD 7850		55040 Mtexels/sec
Radeon HD 4870 512MB		30000 Mtexels/sec
	Difference: 25040 (83%)

Pixel Rate

If using a high screen resolution is important to you, then the Radeon HD 7850 is superior to the Radeon HD 4870 512MB, by far. (explain)

Radeon HD 7850		27520 Mpixels/sec
Radeon HD 4870 512MB		12000 Mpixels/sec
	Difference: 15520 (129%)

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 past the external memory interface in a second. It's calculated by multiplying the bus width by the speed of its memory. If it uses DDR RAM, the result should be multiplied by 2 again. If it uses DDR5, multiply by 4 instead. The better 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 number of texture map elements (texels) that are processed in one second. This is worked out by multiplying the total number of texture units of the card by the core clock speed of the chip. The better the texel rate, the better the graphics card will be at texture filtering (anisotropic filtering - AF). It is measured in millions of texels applied in one second.

Pixel Rate: Pixel rate is the maximum amount of pixels that the graphics chip can possibly record to the local memory in one second - measured in millions of pixels per second. Pixel rate is worked out by multiplying the amount of ROPs by the the core speed of the card. ROPs (Raster Operations Pipelines - also called Render Output Units) are responsible for outputting the pixels (image) to the screen. The actual pixel fill rate is also dependant on many other factors, especially the memory bandwidth of the card - the lower the memory bandwidth is, the lower the ability to get to the max fill rate.