Newsgroups: comp.arch
Path: utzoo!henry
From: henry@zoo.toronto.edu (Henry Spencer)
Subject: Re: processor for graphics terminal [was: PC/AT clones with RISC cpu]
Message-ID: <1990Nov3.235958.21976@zoo.toronto.edu>
Organization: U of Toronto Zoology
References: <1990Nov2.000650.18866@jarvis.csri.toronto.edu> <0093F1A8.A28E4920@KING.ENG.UMD.EDU> <1990Nov3.052952.1786@zoo.toronto.edu> <1990Nov3.150202.27353@ameristar>
Date: Sat, 3 Nov 90 23:59:58 GMT

In article <1990Nov3.150202.27353@ameristar> rick@ameristar (Rick Spanbauer) writes:
>>... Sun normally uses proprietary MMU designs that bear no
>>relation to (e.g.) the "Sparc Reference MMU".  Worse, not only are they
>>proprietary but they are Top Secret, although apparently Sun has entirely
>>forgotten why, since they can't offer any rational reason for it when
>>asked.
>
>	It may be a simple reason, like not wanting users to be able to buy 
>	only SunOS tapes from Sun and then run the binaries on cheap sparc 
>	clones, or to make the job of clone companies harder...

I said "rational reason".  The problem with the idea of keeping it secret
from the competition is that it's not that hard to reverse-engineer the
stuff if you try.  The basic design concepts were published long ago; all
that is being kept secret is the details, exactly the sort of thing that
a competent engineering team could figure out in a month or two, given
a couple of machines to play with and modern tools.  Any would-be clone
company has ample resources to figure this stuff out without Sun's help.
This policy makes life harder only for the legitimate customers.

I can see keeping things like this secret *briefly*, when the machine is
new and hot and it's worth throwing up even small obstacles to the cloners,
but why are the MMU details of the Sun 2 still secret today?
-- 
"I don't *want* to be normal!"         | Henry Spencer at U of Toronto Zoology
"Not to worry."                        |  henry@zoo.toronto.edu   utzoo!henry