Path: utzoo!utgpu!news-server.csri.toronto.edu!bonnie.concordia.ca!uunet!zaphod.mps.ohio-state.edu!think.com!snorkelwacker.mit.edu!bloom-beacon!deccrl!news.crl.dec.com!shlump.nac.dec.com!decuk.uvo.dec.com!hollie.rdg.dec.com!decvax.dec.com!abyss.zk3.dec.com!kenton
From: kenton@abyss.zk3.dec.com (Jeff Kenton OSG/UEG)
Newsgroups: comp.arch
Subject: Re: Vector processors, i860
Message-ID: <544@decvax.decvax.dec.com.UUCP>
Date: 8 Feb 91 14:26:07 GMT
References: <1991Feb3.061217.21988@watdragon.waterloo.edu> <1991Feb03.082253.12458@kithrup.COM> <11770@pt.cs.cmu.edu>
Sender: news@decvax.dec.com.UUCP
Reply-To: kenton@abyss.zk3.dec.com (Jeff Kenton OSG/UEG)
Lines: 38

I received the following reply to a previous post of mine which I thought I
would pass along:


In article <538@decvax.decvax.dec.com.UUCP> you write:
>In article <1991Feb3.061217.21988@watdragon.waterloo.edu>,
>ccplumb@rose.uwaterloo.ca (Colin Plumb) writes:
>|> hsong@nvuxl.UUCP (g hugh song) wrote:
>|> > Why is it so hard to build a UNIX machine with Intel's i860 chip? 
What is
>|> > missing in this chip for building a UNIX machine out of this chip?
>|> 
>|> Return from interrupt.  When the chip takes an exception, it sort of
>|> drops all the bits in the pipleine on the floor and lets software
>|> put the pieces back together.  The code to restart from an interrupt
>|> is, I'm told, 10,000 lines of assembler.
>|> 
>
>I don't believe this number.  It clearly takes some work, but I would guess
>it's more on the order of 100 - 200 instructions.  Anyone know?
>


Sorry, I can't post, but you can post my answer...
It's under 1000 lines (including comments, etc.) for the assembly-level
save and restore code, including all the trap type identification.
Fortunately a whole lot less than 10,000 lines.

Doug Doucette
doug@swdc.stratus.com
Stratus Western Development Center
San Jose, CA


-----------------------------------------------------------------------------
==	jeff kenton		Consulting at kenton@decvax.dec.com        ==
==	(617) 894-4508			(603) 881-0011			   ==
-----------------------------------------------------------------------------