XPost: alt.folklore.computers   
   From: anton@mips.complang.tuwien.ac.at   
      
   Al Kossow  writes:   
   >[RISC] didn't really make sense until main   
   >memory systems got a lot faster.   
      
   The memory system of the VAX 11/780 was plenty fast for RISC to make   
   sense:   
      
   Cache cycle time: 200ns   
   Memory cycle time: 600ns   
   Average memory access time: 290ns   
   Average VAX instruction execution time: 2000ns   
      
   If we assume 1.5 RISC instructions per average VAX instruction, and a   
   RISC CPI of 2 cycles (400ns: the 290ns plus extra time data memory   
   accesses and branches), the equivalent of a VAX instruction takes   
   600ns, more then 3 times as fast as the actual VAX.   
      
   Followups to comp.arch.   
      
   - anton   
   --   
   'Anyone trying for "industrial quality" ISA should avoid undefined behavior.'   
     Mitch Alsup,    
      
   --- SoupGate-Win32 v1.05   
    * Origin: you cannot sedate... all the things you hate (1:229/2)