Abstract: A structure and a method are provided to implement a memory bus arbiter, in which separate priorities are provided to instruction and data reads from the main memory. In one embodiment in a microprocessor with an on-chip cache, the present invention provides an arbiter which yields the memory bus, in decreasing priority order, to an ongoing bus transaction, a "direct memory access" (DMA) request, an instruction read resulting from a cache miss, a pending write request, and a read request, including reference to an uncacheable portion of memory and a data cache miss.