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From: mahler@usl-pc.UUCP (Stephen J. Mahler)
Newsgroups: comp.arch,comp.unix.wizards,comp.os.misc
Subject: Re: Shared libraries (Was: Re: Big Programs Hurt Performance)
Message-ID: <108@usl-pc.UUCP>
Date: Wed, 21-Oct-87 08:57:56 EST
Article-I.D.: usl-pc.108
Posted: Wed Oct 21 08:57:56 1987
Date-Received: Sun, 25-Oct-87 01:49:36 EST
References: <8714@utzoo.UUCP> <286@usl> <73@usl-pc.UUCP> <881@sugar.UUCP>
Reply-To: mahler@usl-pc.UUCP (Stephen J. Mahler)
Organization: Univ. of Southwestern La., Lafayette
Lines: 18
Xref: mnetor comp.arch:2692 comp.unix.wizards:5046 comp.os.misc:311

In article <881@sugar.UUCP> peter@sugar.UUCP (Peter da Silva) writes:
>> DEC machines of PDP design included versions that did not include
>> MMUs. ...  UNIX ran on these machines. ...  It had features between V6
>> and V7 and the only real stripping of the OS was the removal of account
>> "groups" (/etc/group, newgrp, chgrp, etc.).
>
>So tell me... how did they implement fork() without an MMU? Did they do
>addres fixups on running code, or did they require all code be relocatable
>(not an unreasonable request on the PDP-11, by the way, and one place where
>the 11 has the 68000 beat hollow).
>-- 
Only one proc was in memory at a time.  When swtch() was called the
entire proc moved to swap.  Considering the ~ 20K (word) proc space
(small by todays standards ... but reasonable back then) and the
speed of the CPU it made a good match with floppies that were DMA.
On the other hand DECs RX01 floppies were PIO, now that was slow
(but it to was also working at some locations)!
    .... Steve   KF5VH