🚀 go-pugleaf

			     ABSTRACT

   The scalar performance of microprocessors is increasing much faster than
   the floating point performance of floating point coprocessors.  
   Floating point performance is essential for many Fortran applications.  
   The purpose of this note is to encourage microprocessor designers to 
   concentrate more on floating point.

   The Current State of the World
   ------------------------------

   The "big three" microprocessor manufacturers (iNTEL, Motorola and
   National Semiconductor) have all announced 32-bit microprocessors.  
   These chips all have high scalar performance (at least for
   microprocessors).  
   
   Unfortunately the speed of the floating point co-processors has not 
   kept up.  Below are some approximate speeds for the various math 
   coprocessors.  The performance listed is "peak" performance, which 
   assumes that the operands are already in the floating point registers.

      Intel   80287   less than 0.1 MFLOP
      National        0.1 MFLOP
      Motorola        0.3 MFLOP

   Naturally these speeds will vary, depending on clock speed, but there
   are not far off.  None of these coprocessors has performance that is 
   close to 1 MFLOP.

   National has a chip (the 32310) that will allow the 32032 to be
   interfaced with the Weitek floating point ALU and multiply unit.
   This yields 0.8 MFLOPS with math error checking enabled and 1.2 MFLOPS
   with it disabled.  Unfortunately the 32310 solution not only entails a
   significant increase in component price (a 32310, two Weitek chips and
   support logic), but also consumes a lot of board space and power.  Whether 
   the increase in floating point performance justifies these increased 
   costs is arguable.  I would like to get more MFLOPS for my bucks.

   We Need More MFLOPS
   -------------------

   At one time (three years ago) 0.1 MFLOP was considered pretty good
   floating point performance.  This is no longer true.  Floating point
   performance tends to be measured now against the Weitek chips (or AMD or
   Analog Devices etc...) used in bit-slice applications (e.g., 10 MFLOPS).

   The floating point performance available with the Weitek chips would be
   wasted on the current generation of microprocessors.  Even the 
   fastest microprocessors currently available could not feed
   floating point operands to a coprocessor fast enough to keep up with the
   10 MFLOP rate.  What is needed is a coprocessor (or an integrated
   floating point processor) that will yield 1 to 2 MFLOPS.

   So far the only microprocessor that comes close to delivering 1 MFLOP of
   floating point performance is the Fairchild Clipper.  The Clipper has an
   on chip floating point unit rated at about 1 MFLOP.  

   Fortran, despite its many problems, is one of the most widely used 
   programming languages.  Despite the hopes of many computer scientists, 
   Fortran will never disappear (there will just be new versions of 
   Fortran).  The increasing power of microprocessors means that 
   more Fortran applications will be run on microprocessor based 
   systems.  Many Fortran applications are floating point bound, so the 
   increased scalar performance provided by the current generation of 
   32-bit microprocessors will only speed them up fractionally.  For
   these applications floating point performance will be the deciding
   factor.  The microprocessor vendor that realizes the importance of 
   floating point performance, and develops a solution, will capture a 
   large number of designs where Fortran performance is important.


		     Ian Kaplan
		     Loral Dataflow Group
		     Loral Instrumentation
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