Pipelining and performance in the VAX 8800 processor

The VAX 8800 family (models 8800, 8700, 8550), currently the fastest computers in the VAX product line, achieve their speed through a combination of fast cycle time and deep pipelining. Rather than pipeline highly variable VAX instructions as such, the 8800 design pipelines uniform microinstructions whose addresses are generated by instruction unit hardware. This design approach helps achieve a fast cycle time, which is the prime determinan of performance. Some preliminary measurements of cycles per average instruction are reported.