Abstract: Method and apparatus to avoid the code space and time overhead of the software-loop. Loops (repeatedly executed blocks of instructions) are often used in software and microcode. Loops may be employed for array manipulation, storage initialization, division and square-root interpretation, and microinterpretation of instructions with variable-length operands. Software creates loops by keeping an iteration count in a register or in memory. During each iteration of the code loop, software decrements the count, and then branches to the "top" of the loop is the count remains nonzero. This apparatus puts the decrement, compare, and branch-to-top into hardware, reducing the number of instructions in the loop and speeding loop execution. Hardware further speeds loop execution by eliminating the wait for the branch to the top-of-loop instruction. That is, it prefetches the top-of-loop instruction near the bottom of the loop.

Abstract: A method and apparatus for generating a composite image from multiple source images using multiple local masks. Each source image is generated by an image generator. Each image generator has a local mask that indicates which pixels of the source image are to be transmitted to a frame buffer. The local mask may also be used to indicate which pixels of the source image are to be updated by the image generator.

Abstract: A CPU or other graphics processor provides a pixel data stream to a graphics controller over a system bus. The pixel data stream includes a graphics controller address as well as a pixel type tag, which in the presently preferred embodiment comprises 4 bits. In addition to the graphic controller address and pixel type tag, a pixel address and pixel data are provided. The pixel type tag identifies the "type" of pixel data in the data stream supplied to the graphics controller. If the data identified by the pixel type tag corresponds to the type of data which the frame buffer is configured for, then the data provided over the system bus is simply passed through the graphics controller and written at the appropriate pixel address in the frame buffer.