Internal RAW Hazards

An internal RAW (Read-After-Write) data dependency hazard occurs 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 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 3-39). 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.