Radeon HD 4870 2GB vs Radeon HD 7770

Intro

Compare that to the Radeon HD 7770, which has a core clock speed of 1000 MHz and a GDDR5 memory speed of 1125 MHz. It also uses a 128-bit bus, and uses a 28 nm design. It is made up of 640 SPUs, 40 Texture Address Units, and 16 ROPs.

Display Graphs

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Power Usage and Theoretical Benchmarks

Power Consumption (Max TDP)

Radeon HD 7770		80 Watts
Radeon HD 4870 2GB		150 Watts
	Difference: 70 Watts (88%)

Memory Bandwidth

Theoretically speaking, the Radeon HD 4870 2GB is 60% faster than the Radeon HD 7770 in general, due to its greater bandwidth. (explain)

Radeon HD 4870 2GB		115200 MB/sec
Radeon HD 7770		72000 MB/sec
	Difference: 43200 (60%)

Texel Rate

The Radeon HD 7770 should be a lot (more or less 33%) better at texture filtering than the Radeon HD 4870 2GB. (explain)

Radeon HD 7770		40000 Mtexels/sec
Radeon HD 4870 2GB		30000 Mtexels/sec
	Difference: 10000 (33%)

Pixel Rate

The Radeon HD 7770 will be quite a bit (more or less 33%) better at FSAA than the Radeon HD 4870 2GB, and able to handle higher resolutions without slowing down too much. (explain)

Radeon HD 7770		16000 Mpixels/sec
Radeon HD 4870 2GB		12000 Mpixels/sec
	Difference: 4000 (33%)

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 maximum amount of information (measured in MB per second) that can be moved past the external memory interface in a second. It's calculated by multiplying the bus width by its memory clock speed. In the case of DDR type RAM, the result should be multiplied by 2 again. If it uses DDR5, multiply by 4 instead. The better the card's memory bandwidth, the faster the card will be in general. It especially helps with anti-aliasing, HDR and higher screen resolutions.

Texel Rate: Texel rate is the maximum amount of texture map elements (texels) that can be applied per second. This number is calculated by multiplying the total amount of texture units of the card by the core speed of the chip. The better this number, the better the graphics card will be at handling texture filtering (anisotropic filtering - AF). It is measured in millions of texels applied in one second.

Pixel Rate: Pixel rate is the maximum number of pixels that the graphics card can possibly record to the local memory in one second - measured in millions of pixels per second. The number is worked out by multiplying the number of ROPs by the the core speed of the card. ROPs (Raster Operations Pipelines - also sometimes called 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, especially the memory bandwidth of the card - the lower the memory bandwidth is, the lower the ability to get to the maximum fill rate.