Radeon HD 4870 512MB vs Radeon HD 6870

Intro

The Radeon HD 4870 512MB makes use of a 55 nm design. AMD has clocked the core frequency at 750 MHz. The GDDR5 RAM is set to run at a speed of 900 MHz on this particular card. It features 800(160x5) SPUs as well as 40 Texture Address Units and 16 Rasterization Operator Units.

Compare all that to the Radeon HD 6870, which comes with GPU core speed of 900 MHz, and 1024 MB of GDDR5 memory set to run at 1050 MHz through a 256-bit bus. It also features 1120 SPUs, 56 TAUs, and 32 Raster Operation Units.

Price Comparison

Specifications

Memory Bandwidth: Memory bandwidth is the maximum amount of data (measured in megabytes per second) that can be transported across the external memory interface in a second. It is calculated by multiplying the bus width by the speed of its memory. If the card has DDR RAM, it should be multiplied by 2 again. If 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, High Dynamic Range and high resolutions.

Texel Rate: Texel rate is the maximum number of texture map elements (texels) that can be applied in one second. This is worked out by multiplying the total number of texture units by the core speed of the chip. The higher the texel rate, the better the video card will be at texture filtering (anisotropic filtering - AF). It is measured in millions of texels processed in one second.

Pixel Rate: Pixel rate is the most pixels the video card can possibly write to the local memory in one second - measured in millions of pixels per second. The number is calculated by multiplying the amount of colour ROPs by the the core clock speed. ROPs (Raster Operations Pipelines - also called Render Output Units) are responsible for outputting the pixels (image) to the screen. The actual pixel output rate is also dependant on many other factors, especially the memory bandwidth - the lower the bandwidth is, the lower the potential to get to the maximum fill rate.