68k Macs, was Re: Alpha CPUs, was Re: [rescue] i860 Success

Nathan Raymond nate at portents.com
Tue May 4 09:33:36 CDT 2004

Here's a good site to cross-check your recollections of the 68k Mac:


On Mon, 3 May 2004, Patrick Giagnocavo +1.717.201.3366 wrote:

> The original Mac shipped with a 68000.  Later Macs shipped with
> 68020's.

It's not quite that simple... the Mac II (1987) and LC (1990) shipped with
the 68020.  The last 68000 Macs were the Classic (1990) and PowerBook 100

> A smart programmer wrote a tool which Apple bought and distributed for
> free to everyone.  It was called Mode32.

Apple had already developed a software-only solution to the 24-bit 'dirty
ROM' problem in the UNIX OS, AU/X.  AU/X also served as a testbed for
32-bit Application development (it's Finder was the basis of the System 7
Finder).  It's unclear why Apple didn't port their 32-bit clean software
solution from AU/X to System 7 (supposedly there were developers inside
Apple who said it 'couldn't be done').

Initially Mode32 was a commercial product, before Apple licensed it due to
the outcry from users (all early Macs had ROMs on SIMMs but Apple never
released any newer 32-bit clean ROMs except privately to developers).

Connectix had another commercial product called Optima which
brought 32-bit clean to System 6, and Maxima which allows access to 14MB
of RAM in System 6 using 'enhanced 24-bit addressing'.

On Tue, 4 May 2004, Andrew Weiss wrote:

> The Mac II was the only 68020 Mac AFAIK.

You're forgetting the original Mac LC (1990).

On Tue, 4 May 2004, Geoffrey S. Mendelson wrote:

> Todd Carson wrote:
> > I believe it was the SE/30 which was the first to have an '030, and
> > the Mac II which first had an '020.

The II came out in 1987, the IIx in 1988, and the SE/30 in 1989.

> The Mac II had a 68020, a 6881 floating point processor, and a socket for a
> MMU.

68881, actually.

> The Mac IIx had a 68030 and a 6881. It also had a 1.4 meg floppy drive.

68882, actually.

> The SE was a 68000 no MMU (no support on the chip).
> The SE/30 was a MacIIx squeezed into a Mac/SE case. 68030, 68881, and
> one modified NuBus slot (it had the connector on the end instead of the
> bottom of the card).

The SE/30 (1989) is closer to the Mac IIcx (1989) than the IIx (1988).
And the SE/30 did not have a NuBus slot or the logic for NuBus, it only
had a Processor Direct Slot (PDS).  The IIsi was the direct decendant of
the SE/30 (you can take the ROM SIMM from the early IIsi and replace the
SE/30 ROM SIMM to make a 32-bit clean SE/30), and the IIsi could take
NuBus cards if you bought the PDS to NuBus 'adapter' that actually
included the NuBus logic on several chips, along with a 68882 (the IIsi
lacked a 68882, unlike the SE/30).

Nathan Raymond

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