At 8:44 PM -0500 9/21/97, Armen Babikyan wrote:
>for certain macs, a FDHD upgrade was offered, and the chip replacement came
>with a PMMU upgrade. so any mac II you see that has a FDHD, *should* have a
>PMMU installed. they're not dependant on each other, afaik.  i thought
>IIcx's were included...guess not.  maybe i'm thinking of IIx's.

The Mac II was the only Mac that included the socket for the optional PMMU
chip. Since this computer had a 68020 CPU, it required the PMMU chip to run
A/UX or any Mac OS virtual memory scheme. The Mac IIx, the replacement for
the Mac II, upgraded the CPU to a 68030, which has an integrated MMU.
Therefore the IIx didn't have a socket for the PMMU. The Mac IIx also
introduced the 1.4M floppy drives. So, to make a Mac II functionally the
same as a IIx, both the 1.4M floppy support and the PMMU chip had to be
added. That was why they were sold as a kit.

A IIcx is basically a chopped version of the IIx. Since it has the 68030,
it does indeed have the MMU. But the 1.4M floppy support really has nothing
to do with the MMU, as the LC, the Mac Classic, and even some of the later
Mac SEs demonstrate.

Regardless, the IIcx has all the hardware you need to run NetBSD/mac68k.

(Snipped discussion of running System 7.6 on the IIcx.)

>so how *do* i boot an old version of the system on this thing? i'm thinking
>of taking out the battery from the board for a few minutes, but i don't
>know if that would do any good. i'm not getting a second startup chime when
>i start up with command-option-P-R, either. anyone know why?

If you don't have a version of System 7.5 that will work on the IIcx, you
can download System 7.0.1 from Apple's software updates servers. This
version of the system will support the Mac side software needed to install
and run NetBSD. If you aren't going to use the Mac side very much, you
don't have to worry about the what version of the system software you are
using.

You probably aren't getting the second start up chime when you start up
with command-option-P-R, because the system software sees that the hardware
isn't supported before the "zap the parameter RAM" code is run.

By the way, I have a very similar hardware setup. Once you get through the
setup, everything should work great.


Eric Damien Berna
eric@thiel.com

Mac IIcx running NetBSD/mac68k version 1.2.1