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From: ucbesvax.turner@ucbcad.UUCP
Newsgroups: net.arch
Subject: Re: RISC operating system - (nf)
Message-ID: <116@ucbcad.UUCP>
Date: Tue, 21-Jun-83 07:02:40 EDT
Article-I.D.: ucbcad.116
Posted: Tue Jun 21 07:02:40 1983
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#R:uiucdcs:27800010:ucbesvax:12800002:000:1522
ucbesvax!turner    Jun 21 01:06:00 1983


Some comments on the UNIX/RISC comparison:

    - UNIX as a RISC OS?  I think this is mostly an outgrowth of the
      decision to have (essentially) two kinds of files: i-nodes and
      strings of bytes in blocks.  It is worth noting, however, that
      one does result in an efficient file-system by any means.  It is
      one of UNIX's recognized failings.  The remedies for this are
      by no means simple.  (Although some of these DO help enormously.)
    
    - The idea behind RISC (if I understand it correctly) is that there
      is performance to be gained in simplifying the control logic.
      In the case of Berkeley RISC's, the case had been made fairly well.
      (It is amusing when uP designers from industry look at the RISC I/II
      layouts and search vainly for ROM.)  In UNIX, however, the "control
      logic" is undeniably simpler than that of systems of supposedly
      equivalent power, but where is the performance gain?
    
    - In RISC I/II, the space that might be filled with microcode ROM is
      instead taken up by register files.  The case for RISCs lies almost
      entirely in what one does with leftover capacity.  At Berkeley, this
      space was taken up by what is essentially a very specialized on-chip
      cache memory.

Well, I didn't start out with any particular point to make.  I don't think
that the comparison is unduly stretched.  Perhaps the real performance
gain in UNIX is that it tends to optimize programming.

	Michael Turner
	ucbvax!esvax.turner