A coherent computer system includes a memory shared by a processor and a coherent accelerator device (CAD). The memory includes a work queue directly accessible by the accelerator functional unit (AFU) within the CAD and by the processor utilizing the same effective addresses. The coherent computer system provides accelerator functionality when the accelerator is unavailable by implementing a virtual AFU to carryout accelerator function while the AFU is unavailable. The virtual AFU is a functional logical equivalent of the AFU and is coherent with the processor. When the AFU becomes available, the virtual AFU is disabled and the accelerator is enabled to allow the accelerator to carryout accelerator functionality.