https://rbelmont.mameworld.info/?p=1436

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This page will include WIP screenshots and other fun stuff for MAME(tm),
M1, and whatever else I'm working on.

5/15/2021

Mac the Knife

We've had lots of movement so far in 2021 on the 80s/90s Macintosh
drivers, so let's talk about it a bit. Things started off with my
splitting the large, ugly, unwieldy mac.cpp driver into several new
drivers. The "classic" black and white 68000 Macs went to mac128.cpp,
the Portable and PowerBook 100 went to macprtb.cpp, the 68030
PowerBooks went to macpwrbk030.cpp, the Quadra 700 went to
macquadra700.cpp, and the PowerMac 6100 went to macpdm.cpp. (PDM is
"PiltDown Man", the codename of the 6100; early PowerMacs were named
for famous scientific hoaxes).

[0001]

All of these drivers got cleanup and modernization along the way. The
Portable and PowerBook 1xx series got improved video emulation and we
now emulate their Power Management Units by running their original
Apple code, which are microcontrollers that handle power management
and control and also Apple Desktop Bus interfacing. This is thanks in
part to improved emulation of the Mitsubishi M50753 microcontroller
these PMUs are based on, by AJR and myself. There is also partial ADB
support working now on the Portable and PowerBook 100.

As part of that work, we needed to slow the ADB simulation down to
match the speed of real hardware, and Olivier Galibert came up with a
more accurate way to emulate the wait states incurred by the Mac's
main CPU when it was accessing certain chips in the system. This
exposed an issue with our 68HC05EG emulation where it was using the
wrong cycle counts; fixing that brought the emulated ADB bit cells
into spec.

[0003]

The next big step was brand new emulation by Olivier Galibert of the
4 major Apple floppy disk controllers, the IWM, SWIM, SWIM2, and
SWIM3. Emulating these enabled support for reading copy-protected
images (also on the Apple IIgs) as well as 1.44MB high-density
floppies. True to hardware, our SWIM and SuperDrive emulation
supports 400K, 800K, and 1.44MB floppies interchangeably, and you can
read/write 800K disks on the 1.44MB drive. We also have a feature for
the Apple IIgs where when you create a new floppy image in MAME's
file manager menu, it now gives you the option of having it be
pre-formatted for the ProDOS file system, which saves time formatting
the disk in the emulation. We're hoping to extend to the Mac's MFS
and HFS disk formats in the future.

After that, I worked with Patrick Mackinley to get the Mac Plus
working with our new bit-level SCSI emulation and cycle-accurate
NCR5380 controller chip. This allowed the Mac Plus to use our latest,
most accurate SCSI emulation, but due to some problems that were
thought to be insurmountable, later Macs weren't allowed in. Olivier
Galibert noticed in the code that in fact the hardware wasn't being
quite as devious as we had thought, and AJR came up with a scheme
which allowed all of the emulated Macs to use the newer and more
accurate SCSI subsystem. This opened up the possibility of finally
supporting CD-ROM drives on the Mac, but early attempts didn't work.
Al Kossow provided some SCSI bus snooping logs of a real Mac booting
from a CD-ROM and I was able to modify our SCSI CD-ROM to comply with
Apple's specifications. As a result, most of our Macs now can both
read and boot from CD-ROMs (this will be in MAME 0.232).

[0006]

To match the added capabilities of the Mac drivers, the documentation
has been greatly expanded in the form of a system-specific wiki page,
similar to the one for the Apple II series. The page is still a
work-in-progress but it hopefully already provides useful
information.

A graphical install guide which shows how to format a new hard disk
image and install the Mac OS in the driver is available. Note that
the instructions WILL NOT work with the current release of MAME; you
need either a build of an up-to-date GitHub pull or to wait for MAME
0.232.

[0015]

Posted by Arbee in General @ 9:32 pm -

Comments are closed.

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