Path: utzoo!censor!geac!jtsv16!uunet!cs.utexas.edu!tut.cis.ohio-state.edu!pt.cs.cmu.edu!a.gp.cs.cmu.edu!koopman
From: koopman@a.gp.cs.cmu.edu (Philip Koopman)
Newsgroups: comp.lang.forth
Subject: Re: SC32 performance and availability
Summary: RTX vs. SC32 comparisons
Message-ID: <6994@pt.cs.cmu.edu>
Date: 16 Nov 89 15:58:01 GMT
References: <931@mtk.UUCP> <3891@aplcen.apl.jhu.edu>
Distribution: usa
Organization: Carnegie-Mellon University, CS/RI
Lines: 42

In article <3891@aplcen.apl.jhu.edu>, mef@aplcen.apl.jhu.edu (Marty Fraeman) writes:
 
> From: mef@aplcen.apl.jhu.edu (Marty Fraeman)
> Subject: SC32 performance and availability
 
> Estimating the performance of chips under development is
> of course not likely to be very accurate.  But based on
> the talk given by Phil Koopman at the Rochester Forth
> conference two years ago and by Rick Van Norman at the
> conference this year, the architecture of the RTX 4000 
> is significantly different from either the RTX 2000 or the
> SC32.  A comparison of the two approaches to supporting
> Forth in hardware would certainly be an interesting study
> but I don't believe the outcome is at all a forgone conclusion.
> Perhaps Phil could enlighten us.
 
A comparison between the RTX 32P and the RTX 2000 showed
that they took about the same number of clock cycles to execute a mix
of Forth instructions.  The minimum time to execute an instruction
on the RTX 32P was 2 clocks, but it made up for this by supporting
higher-level instructions (e.g. ROT and 2OVER ) and by combining
subroutine calls with opcodes "for free".  The RTX 4000 takes
fewer clock cycles for the average instruction than the RTX 32P.
It would be premature to claim that this does more than
equal the increase in power of the SC32 over the RTX 2000.
So, I agree that the jury is still out.
 
BUT, number of clock cycles is not the entire issue.  For embedded
real time control, memory chip speed is usually a consideration
because of a combination of cost, power/cooling, and size concerns.
The 32-bit RTX series uses 2 clocks per memory cycle
instead of 1 clock per memory cycle.  That means that if the limiting
factor in your system is memory chip speed, you get at least twice
the clock frequency with the 32-bit RTX family than with the RTX 2000 or
SC32.  The RTX 4000 is being optimized for total system solution
effectiveness, *not* raw speed at any cost.
 
  Phil Koopman                koopman@greyhound.ece.cmu.edu   Arpanet
  2525A Wexford Run Rd.
  Wexford, PA  15090
Senior Scientist at Harris Semiconductor.
I don't speak for them, and they don't speak for me.