Compare any two graphics cards:
Radeon HD 4830 512MB vs Radeon HD 4850 X2 1GB
IntroThe Radeon HD 4830 512MB uses a 55 nm design. AMD has set the core frequency at 575 MHz. The GDDR3 RAM works at a frequency of 900 MHz on this particular card. It features 640(128x5) SPUs along with 32 TAUs and 16 Rasterization Operator Units.
Compare those specifications to the Radeon HD 4850 X2 1GB, which makes use of a 55 nm design. AMD has set the core speed at 625 MHz. The GDDR3 memory works at a frequency of 993 MHz on this particular model. It features 800(160x5) SPUs as well as 40 TAUs and 16 ROPs.
Power Usage and Theoretical Benchmarks
Power Consumption (Max TDP)
Theoretically speaking, the Radeon HD 4850 X2 1GB is 121% quicker than the Radeon HD 4830 512MB in general, due to its greater data rate. (explain)
Texel RateThe Radeon HD 4850 X2 1GB is quite a bit (more or less 172%) more effective at texture filtering than the Radeon HD 4830 512MB. (explain)
Pixel RateIf using lots of anti-aliasing is important to you, then the Radeon HD 4850 X2 1GB is a better choice, and very much so. (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: Memory bandwidth is the largest amount of data (in units of megabytes per second) that can be transported across the external memory interface in a second. It's worked out by multiplying the card's interface width by its memory clock speed. If it uses DDR RAM, it should be multiplied by 2 once again. If it uses DDR5, multiply by 4 instead. The higher the bandwidth is, the faster 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 figure is calculated by multiplying the total amount of texture units of the card by the core clock speed of the chip. The higher 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 a second.
Pixel Rate: Pixel rate is the maximum amount of pixels the video card can possibly write to the local memory in a second - measured in millions of pixels per second. The figure is calculated by multiplying the number of colour ROPs by the the core speed of the card. ROPs (Raster Operations Pipelines - sometimes also referred to as Render Output Units) are responsible for filling the screen with pixels (the image). The actual pixel rate is also dependant on quite a few other factors, especially the memory bandwidth - the lower the bandwidth is, the lower the potential to get to the max fill rate.