Internal RAW Hazards

An internal RAW (Read-After-Write) data dependency hazard will occur when the result of an FPU instruction is not available at the time it is selected as the source operand (F-reg) of a subsequent FPU instruction. The affected instruction will be stalled in the RD-stage until such time that the hazard is resolved.

In order to mitigate the hazards, the coprocessor includes data forwarding paths between the FPU execution result data output and the coprocessor RD-stage (as shown in Figure 3-8). This path will forward the write data value should the write and read instructions target a common register. Forwarding as soon as the result data is available (i.e., prior to the FPU register write) will help mitigate the impact of the hazard.