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!