csh pgrp problem

[Chris Torek]

In article <184 at sunquest.UUCP> terry at sunquest.UUCP (Terry Friedrichsen) writes:
>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().

As I heard it, the model was the 750, and it had something to do with
peculiar addressing modes and stack pages (maybe something like movc3 with
an (sp)+ argument :-) ).  Instruction restart after a fault did not
always work right.

If this is correct, it would explain why not `write off that VAX': until
recently, monet.berkeley.edu (a VAX-11/750) was *the* BSD development
machine.  (It also had---and still has---only 2 MB of memory.  The
new development machine is about 6 VAX MIPS---a 750 is about .6 or .7
---and has 16 MB.  Somehow I suspect 4.4BSD will have a more cavalier
attitude towards CPU and memory usage :-/ . . . .)
-- 
In-Real-Life: Chris Torek, Univ of MD Comp Sci Dept (+1 301 454 7163)
Domain:	chris at mimsy.umd.edu	Path:	uunet!mimsy!chris