Perhaps the main reason why AMD and Nvidia develop dual-processor graphics cards is that they want to emphasize their superiority over the competitor, so such products are, as a rule, based on expensive top-end GPUs. Clock rates and even functional subunits may be sacrificed in order to keep the power consumption and heat dissipation of a dual-processor graphics card within reasonable limits, yet formally AMD Radeon HD 6990 and Nvidia GeForce GTX 590 are indeed based on the fastest GPUs available. Well, most rules have exceptions. PowerColor, a subsidiary of TUL Corporation, has taken on the risk of developing a dual-processor graphics card with midrange rather than top-end GPUs. The product is called PowerColor Radeon HD 6870X2.