XPost: alt.comp.os.windows-11   
   From: not.email@all.invalid   
      
   On Fri, 21 Feb 2025 19:30:50 +0000, Ant wrote:   
      
   > In alt.comp.os.windows-11 Mark Lloyd  wrote:   
   >> On Fri, 21 Feb 2025 12:11:53 +0100, Carlos E.R. wrote:   
   >   
   >> [snip]   
   >   
   >> > Yes, an optional separate coprocesor was used initially. If it was   
   >> > not inserted, an operation trying to use a coprocesor instruction   
   >> > would raise an exception, which would be attended and the instruction   
   >> > emulated in software by the program, which was significantly slower.   
   >   
   >> IIRC, the 286 was the first to have that exception, although there were   
   >> programs to emulate it on older systems. If I remember right, the turbo   
   >> C compiler would replace every floating point instruction with a call   
   >> to a routine that checked for a FPU. If it found one it would replace   
   >> that call with the FPU instruction and return to a few bytes earlier to   
   >> run that instruction, otherwise it would emulate it.   
   >   
   >> [snip]   
   >   
   > What about 386SX? IIRC, it didn't have a coprocessor like DX. I can't   
   > remember!   
      
   No 386 had a coprocessor. You could add a 387 to the system (I don't   
   remember if there was a 387SX). IIRC, it was also possible to use a 287.   
      
   The difference between 386SX and 386DX was a limited (24-bit instead of   
   32-bit) address bus, and a multiplexed (32-bit) data bus.   
      
   It was with the 486 that the DX meant it had a coprocessor. There was also   
   a 486DX2 that ran at a doubled clock speed.   
      
   --   
   Mark Lloyd   
   http://notstupid.us/   
      
   "Two great European narcotics, alcohol and Christianity." [Nietzsche,   
   Twilight of the Idols, "What the Germans Lack," aph. 2 (1889)]   
      
   --- SoupGate-DOS v1.05   
    * Origin: you cannot sedate... all the things you hate (1:229/2)