🚀 go-pugleaf

mmm@cup.portal.com (Mark Robert Thorson) writes:
}I write:
}>    Depends on what you call a MIP.  I just did the following on a VS2000
}>    (basically a uVAX II)
  
}>           MOVL    #100000,R2  ; do 10 million instructions
}>    10$:   NOP                 ; \
}>           <97 more NOPs>      ;  \ 100 instructions
}>           DECL    R2          ;  /
}>           BNEQ    10$         ; /
  
}>    and got a result of 2.25 seconds, that works out to 4.444 MIPs
  
     [386 machine returns instantly on 1 & 10 million iter. loops]
 
}Now he knew something was wrong. ...  compiler ...  removed the loop

     Are there optimizing assemblers!?!?  
     Anyhow, MACRO-32 doesn't, the loop is actually there.
     If memory serves, the uVAX instruction prefetch is big enough for
     eight NOPs (and some of the more `hideous' instructions don't even
     fit) which probably explains this `unusual' performance.
     (The VS3200 was > 10 MIPS :-).  Assuming uVAXII == 1MIP, it looks
     like the average VAX instruction takes 4 1/2 cycles on a uVAXII.
     (Compare with the VAX9000 which appears to be just over 1 cycle/instr).

John Hascall  /  hascall@atanasoff.cs.iastate.edu