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Path: utzoo!linus!security!genrad!decvax!duke!unc!mcnc!ncsu!fostel
From: fostel@ncsu.UUCP
Newsgroups: net.micro
Subject: RE: P-system slow
Message-ID: <2348@ncsu.UUCP>
Date: Thu, 22-Sep-83 12:48:51 EDT
Article-I.D.: ncsu.2348
Posted: Thu Sep 22 12:48:51 1983
Date-Received: Fri, 23-Sep-83 21:15:22 EDT
Lines: 18



    Yes, the P-system IS slow. Someone suggested that the old saw about
    90% of the time in 10% of the code was applicable here.  False.  The
    P-system is orders of magnitude slow.  My 68000 based P-system can do
    only about 10K cycles of a "i=i+1;" loop body in a second.  You are
    not going to get around that without circumventing the P-system.  There
    are also architectural problems regarding the address space: 16-bit.
    The usual trick of writing some portion in ASM code is very awkward,
    since while you can call ASM from Pascal, the result is substantially
    larger code (p-code IS small) which is a real problem in 64K, and
    severe design constraints.  You have to write Lots of asm code, not
    just a crucial loop to save 50%.  You can not re-enter the P-system
    from the ASM code except by returning so you can not use any of the
    units for utility purposes within non-critical portion of slow loops ...
    But the key point is that it is SOOOO slow that massive ASM code is
    required to avoid any weak links in the performance.
    ----GaryFostel----