>> I was really disappointed/shocked in the performance numbers Scott Edwards
>> quoted in the article; they were something like 1,000x slower than what I
>> would consider a "decent" compiler (I seem to remember that a hand-written
>> assembler could be as much as 1,400x better) for the speed the PIC was
>> running at.  Now, it is 10-50x better than the STAMP, but it's really pretty
>> slow.
>
>Which Pic BASIC was he talking about?  PBASIC from Parallax is an
>interpreter.  The "compile" option merely copies the interpreter and the
>P-Code into a PIC.

Sorry for taking so long to reply; I had to find the original article.

It's the Micro Engineering Labs BASIC - for $100.00.

The article is in Scott Edward's April 1996 "Stamp Applications" of Nuts &
Volts.

In it, Scott shows the section of code:

  again:
   b1 = b1 + 1                  ;  increment b1
   toggle 0                     ;  toggle pin 0
   goto again

and then goes on to give the following performance results:

  BS1, 4 MHZ            479 Hz
  .
  :
  16C84, compiled 4 MHZ 7215 Hz


Now, my thought was that any decent compiler would produce the following code:

again
  incf   b1                     ;  increment b1
  movlw  0x01                   ;  toggle pin 0
  xorwf  PORTB                  ;  Assume pin 0 is in PORTB
  goto   again

This can be improved to:

  movlw  0x01                   ;  Setup Pin to Toggle
again
  incf   b1                     ;  increment b1
  xorwf  PORTB                  ;  toggle pin 0
  goto   again

Although while I would expect this type of optimization for a workstation
compiler, I wouldn't think that it would be reasonable for a Hobbyist one.

The first loop takes five instruction cycles to run (the second four) - five
instructions running at 4 Mhz (1 MHz Instruction cycle frequency) means that
the loop would run at 200 KHz.


I guess I exaggerated a bit for the relative improvement - I was talking
about 1,000x when I should have said 30x.

But, I think you can see that there is area for concern/improvement.  Not
only in terms of speed, but also in terms of instruction space; what is the
PIC executing during this loop?

>There are also one or two true Pic BASIC compilers out there that produce
>native PIC code.
>
>The latter should be much faster than the former.

According to the article, this Compiler is creating native code.

myke

Today, the commercial sector is advancing computer and communication
technology at a breakneck pace.  In 1992, optical fiber was being installed
within the continental U.S. at rates approaching the speed of sound (if
computed as total miles of fiber divided by the number of seconds in the year).

Aviation Week and Space Technology, October 28, 1996