Subject: Re: PMMU & 40 MB HD(was: IDE Support...)
To: None <mattias.andersson@mailbox.swipnet.se>
From: Ken Nakata <kenn@eden.rutgers.edu>
List: port-mac68k
Date: 03/11/1998 01:37:59
On Tue, 10 Mar 1998 22:04:03 +0000,
Mattias Andersson <mattias.andersson@mailbox.swipnet.se> wrote:
> Colin Wood wrote:
> > > I_ve serious plans to ask for the MC68882 PMMU for my Mac II to be able
> > > to run NetBSD
> > > 1.3! Does 1.1 work without a PMMU?
> > 
> > No.  NetBSD/mac68k has _always_ required a PMMU on the Mac II.
> 
> But on the info sites about versions 1.0-1.3, it says nothing about the
> PMMU
> on the first BSD version (ie 1.0 or 1.1)! Why is this?

Ur, an error in documentation?

> All BSD's require a PMMU even if the infopages does not tell this?

Yes, they most certainly do.  Without it, there's no way to implement
demand paging virtual memory on the 68k (with some rare, obscure
exceptions which don't appy to mac68k).  But the thing is, you get one
built into the 68030 and 68040 CPUs so you don't have to buy a PMMU if
you got one of those.  Of course, the 68020 lacks it...

> Is it totally impossible the get 1.0 to work with a 40 MB HD? 

Why bother with 1.0?  1.3 INSTALL tells us you should be able to
install the minimal system onto a 40MB partition.  If you're trying to
get away without getting a PMMU, I'm afraid you can forget about it.
You have to get either a PMMU or a CPU accelerator with 68030 or
68040.  It's been a while since Daystar discontinued their line of 68k
CPU accelerators, but there may be other companies, such as Sonnet and
DiiMo, still selling such things.  Then again, you might find a used
030 or even 040 Mac cheaper than the upgrade options...  "You never
know until you try" (Scott Adams)

Good luck,

Ken