Newsgroups: comp.realtime
Path: utzoo!utgpu!cunews2!cunews!alfred!greg
From: greg@organia.sce.carleton.ca (Greg Franks)
Subject: Re: What is the future of realtime and RISC?
In-Reply-To: scott@nbc1.ge.com's message of Wed, 15 May 91 21:04:30 GMT
Message-ID: <GREG.91May23104721@organia.sce.carleton.ca>
Sender: news@ccs.carleton.ca (news)
Organization: /home/organia/greg/.organization
References: <1991May15.210430.1134@nbc1.ge.com>
Date: 23 May 91 10:47:21

In article <1991May15.210430.1134@nbc1.ge.com> scott@nbc1.ge.com (Scott Barman) writes:

   I have been looking into realtime for automation projects here and
   learning a lot about the industry and what realtime really is.  But like
   everything else, once the box is open the questions follow.  Before I
   can even think about recomemending a system to use here I need to
   consider the realtime world and RISC processors.

   All the realtime software vendors I've spoken with tell me that the
   Motorola 680x0 architecture is still the dominant one used in the
   realtime world.  But some admit to seeing an increase in requirements
   for RISC processors.  The AMD 29K and Intel i860 and i960 seem to be
   making some inroads, but most say 85% of their business is Motorola
   CISC-based.  There is some promise of SPARC and the 88K is not getting a
   lot of play.

   OK, I've presented only a part of the questions I have.  Let's open up
   the discussion and see what happens!


I think one important factor is cost.  RISC chips are still rather
pricy, whereas 68000's are practically a commodity item these days.

Real time systems use *REAL* memory, so they don't need fancy memory
systems.  Virtual memory is virtually unheard of (and usually
undesired because of the headaches of swapping pages in and out and
the effects of latency that paging causes).  Furthermore, fewer chips
in the memory subsystem means less real estate and lower costs.  I
believe that 29000's are pretty friendly when it comes to el-cheapo
memory design, whereas I don't think that can be said about 88000s.
This factor may explain the 29000's popularity.

Finally, real time systems tend to have a lot of light weight
processes that communicate with one and another; the processes do not
spend lots of CPU time crunching numbers.  Chips that can switch state
quickly will be at an advantage.



--
Greg Franks, (613) 788-5726               | "The reason that God was able to    
Systems Engineering, Carleton University, | create the world in seven days is   
Ottawa, Ontario, Canada  K1S 5B6.         | that he didn't have to worry about 
greg@sce.carleton.ca  ...!cunews!sce!greg | the installed base" -- Enzo Torresi  
