On Mon, 17 Nov 2003, Dave McGuire wrote:

>    Do you mean the machine cycle?  Some processors (mostly CISC ones)
> take multiple clock cycles to execute an instruction, and some take
> varying numbers of clock cycles depending on the instruction.  As an
> example, the Intel 8051 (I mention this one because I happen to be
> doing some cycle counting on an 8051-based system at the moment) uses
> 12 clock cycles per machine cycle, and anywhere from one to three
> machine cycles per instruction.

The VARM doesn't go into that much detail of categorizing the different
cycle times, but it's quite possible given in machine cycles.  It states
things like the following:

 "The MicroVAX-II computer sytem is the first VAX with the processor on
  a single chip. [...] The CPU and FPU are implemented in custom 3 micron
  NMOS technology running at 200 ns cycle time."  VARM, 2nd Ed., p.539.

-brian.