The PERQ CPU was a microcoded discrete logic design, rather than a microprocessor. It was based around 74S181 bit-slice ALUs and an Am2910 microcode sequencer. The PERQ CPU was unusual in having 20-bit wide registers and a writable control store (WCS), allowing the microcode to be redefined.[4] The CPU had a microinstruction cycle period of 170 ns (5.88 MHz).[5]"
https://en.wikipedia.org/wiki/PERQ
>"Processor
The PERQ CPU was a microcoded discrete logic design, rather than a microprocessor. It was based around 74S181 bit-slice ALUs and an Am2910 microcode sequencer. The PERQ CPU was unusual in having 20-bit wide registers and a writable control store (WCS), allowing the microcode to be redefined.[4] The CPU had a microinstruction cycle period of 170 ns (5.88 MHz).[5]"