Editing PERQ (section)

=== Processor ===
The PERQ [[central processing unit|CPU]] was a [[microcode]]d [[transistor–transistor logic|discrete logic]] design, rather than a [[microprocessor]]. It was based around [[74S181]] [[bit-slice]] [[arithmetic logic unit|ALU]]s and an [[AMD Am2900|Am2910]] [[Microsequencer|microcode sequencer]]. The PERQ CPU was unusual in having 20-bit wide [[Processor register|registers]] and a writable [[control store]] (WCS), allowing the microcode to be redefined.<ref name="hardware-faq">{{cite newsgroup
 | title = PERQ 2 Hardware FAQ (long)
 | author = Tony Duell
 | date = 1993-10-12
 | newsgroup = alt.sys.perq
 |message-id= 12OCT199321195696@siva.bris.ac.uk
 | url = http://groups.google.com/group/alt.sys.perq/msg/d15c89bb70505499?hl=en
 | accessdate = 2008-12-02
}}</ref> The CPU had a microinstruction cycle period of 170 [[Nanosecond|ns]] (5.88&nbsp;MHz).<ref name="sus-leaflets-1985">[http://www.chilton-computing.org.uk/acd/sus/perq_pr/p017.htm PERQ Publicity: ICL's PERQ Leaflets 1985]</ref>