Path: utzoo!attcan!uunet!sunquest!terry
From: terry@sunquest.UUCP (Terry Friedrichsen)
Newsgroups: comp.unix.wizards
Subject: Re: csh pgrp problem
Summary: fork  vfork  folklore  hack  DEC strikes again
Message-ID: <184@sunquest.UUCP>
Date: 17 Aug 89 17:41:05 GMT
References: <712@skye.ed.ac.uk> <920@legato.LEGATO.COM>
Organization: Sunquest Information Systems, Tucson
Lines: 19

In article <920@legato.LEGATO.COM>, mojo@legato (Joseph Moran) writes:
> Folklore
> has it that vfork was created solely for csh because of the performance
> costs of csh doing Unix fork's in a paged environment without
> copy-on-write.

And WHY was there no copy-on-write?  In "Design and Implementation of
4.3 BSD" (title paraphrased from memory), the authors write that copy-on-write
was considered and abandoned because a microcode bug in one model of VAX
made it questionable that copy-on-write could be reliably implemented.

They don't identify the model, though, so it's hard to say whether it would
have been better to write off that VAX instead of writing vfork().

Terry R. Friedrichsen
TERRY@SDSC.EDU  (alternate address)

Disclaimer:  the company doesn't read my mail, so it can't possibly know
		what I'm saying!