Path: utzoo!mnetor!uunet!steinmetz!sungoddess!oconnor
From: oconnor@sungoddess.steinmetz (Dennis M. O'Connor)
Newsgroups: comp.arch
Subject: Re: Longer quote, RPM-40 performance
Message-ID: <9759@steinmetz.steinmetz.UUCP>
Date: 2 Mar 88 15:59:17 GMT
References: <9732@steinmetz.steinmetz.UUCP>
Sender: news@steinmetz.steinmetz.UUCP
Reply-To: sungoddess!oconnor@steinmetz.UUCP
Organization: GE Corporate R&D Center
Lines: 52
Keywords: DAIS, 14 MIPS, General Electric

An article by mash@winchester.UUCP (John Mashey) says:
] In article <...> sunset!oconnor@steinmetz.UUCP writes:
] > [...] What specifically does it lack
] >that indicates it wasn't built for UNIX ?
] 
] But, if people want to claim that it's a good UNIX engine,
] it would be nice to know:
] 	a) How you use the MMU to do a modern UNIX?

It doesn't have an MMU : it has a "process address space" scheme.
You have to add a full MMU if you want one, just like a MC68010

] 	b) How you turn the SRAM into a cache, because NOBODY cares about
] 	a workstation whose memory is limited to the size of SRAM you
] 	can drive off the CPU? (and what the performance hit is?)

Go back to the original reason for inventing caches. A cache,
originally, was INDISTINGUISHABLE from main memory to the CPU.
So what's the problem with substituting a cache-backed-up-with-DRAM
for the high-speed RAM that's there ?

] 	c) How much of a performance hit one takes from the various
] 	design choices when trying to use it in the general environment?



] 	d) Any benchmark numbers at all, for real programs of substance,
] 	even run on simulators?  Can't we EVER get some real numbers?

I didn't know it was benchmarks that made an architecture suitable
for UNIX. :-) Benchmarks are by nature a MEASURE, not a property,
of a computer architecture's suitablility to a problem. And remember,
no matter where you go,  "Lack of Proof is Not Proof of Lack." WE did
NOT claim it WAS a good UNIX box; YOU claimed it WASN'T. All that
anyone at GE did ( Bill Davidsen in fact, not one of the RPM40 team,
but a person with fair knowledge of the project ) was express a
DESIRE to see the RPM40 in a "UNIX box". So the burden of proof is
on YOU to back up your claim that it isn't suited to one.
 
] Just out of curiosity, is the RPM intended for ADA, or C, ... or assembler?

Ada, which is NOT an acronym, and therefor should not be in all-caps.
But this is a picky point, which you probably knew, eh ? Ada is a
registered trademark of the U.S. Goverment - Ada Joint Program Office. 
Yes, there WHERE design decisions that resulted from this choice.

] -john mashey	DISCLAIMER: <generic disclaimer, I speak for me only, etc>

--
    Dennis O'Connor			      UUNET!steinmetz!sunset!oconnor
		   ARPA: OCONNORDM@ge-crd.arpa
   (-: The Few, The Proud, The Architects of the RPM40 40MIPS CMOS Micro :-)