Compare any two graphics cards:
Radeon HD 4870 2GB vs Radeon HD 4870 X2
IntroThe Radeon HD 4870 2GB uses a 55 nm design. AMD has set the core frequency at 750 MHz. The GDDR5 memory runs at a speed of 900 MHz on this specific model. It features 800(160x5) SPUs as well as 40 Texture Address Units and 16 ROPs.
Compare those specs to the Radeon HD 4870 X2, which has a core clock frequency of 750 MHz and a GDDR5 memory speed of 900 MHz. It also makes use of a 256-bit memory bus, and makes use of a 55 nm design. It is comprised of 800(160x5) SPUs, 40 Texture Address Units, and 16 Raster Operation Units.
Power Usage and Theoretical Benchmarks
Power Consumption (Max TDP)
Performance-wise, the Radeon HD 4870 X2 should in theory be quite a bit superior to the Radeon HD 4870 2GB overall. (explain)
Texel RateThe Radeon HD 4870 X2 is much (approximately 100%) more effective at anisotropic filtering than the Radeon HD 4870 2GB. (explain)
Pixel RateThe Radeon HD 4870 X2 will be much (more or less 100%) faster with regards to full screen anti-aliasing than the Radeon HD 4870 2GB, and also will be able to handle higher screen resolutions while still performing well. (explain)
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.
One or more cards in this comparison are multi-core. This means that their bandwidth, texel and pixel rates are theoretically doubled - this does not mean the card will actually perform twice as fast, but only that it should in theory be able to. Actual game benchmarks will give a more accurate idea of what it's capable of.
Please note that the price comparisons are based on search keywords - sometimes it might show cards with very similar names that are not exactly the same as the one chosen in the comparison. We do try to filter out the wrong results as best we can, though.
Memory Bandwidth: Bandwidth is the largest amount of data (in units of MB per second) that can be transported over the external memory interface in one second. It is calculated by multiplying the card's bus width by the speed of its memory. If the card has DDR memory, it must be multiplied by 2 again. If it uses DDR5, multiply by 4 instead. The higher the memory bandwidth, the better 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 worked out by multiplying the total number of texture units by the core speed of the chip. The higher this number, the better the video card will be at texture filtering (anisotropic filtering - AF). It is measured in millions of texels in a second.
Pixel Rate: Pixel rate is the maximum number of pixels that the graphics card can possibly write to its local memory in a 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 - also called Render Output Units) are responsible for filling the screen with pixels (the image). The actual pixel fill rate is also dependant on many other factors, most notably the memory bandwidth - the lower the bandwidth is, the lower the ability to get to the maximum fill rate.