Macintosh Plus for the MiSTer Board

This is a port of the Plus Too core from MiST which is the port of the Plus Too project.

I've tried to optimize the code by converting to synchronous style and fixing some glitches and instabilities.

Usage

• Copy the *.rbf onto the root of SD card
• Copy boot0.rom & boot1.rom (Plus and SE ROM files) to MacPlus folder
• Copy disk images in dsk format (e.g. Disk605.dsk) to MacPlus folder

After a few seconds, the floppy disk icon should appear. Open the on-screen display using the F12 key and select the a disk image. The upload of the disk image will take a few seconds. If a bootable system is found on disk, a smiling Mac icon will appear. MacPlus will then begin booting into the desktop.

Floppy disk support

Internal and external floppy disk drives are both supported. The first and second entries in the OSD correspond to the internal and external floppy disk drives, respectively.

Floppy disk images need to be in raw disk format (a.k.a. DiskDup format) with a .dsk extension. Single-sided 400k disk images must be exactly 409,600 bytes in size. Double-sided 800k disk images must be exactly 819,200 bytes in size. Disk Copy 4.2 files are not currently supported. They are largely the same as raw disk format, but include an additional 84-byte header. A tool to convert DC42 format to dsk is available here.

Currently, floppy disk images are not writable within the core.

Floppy disk images cannot be loaded while the Mac accesses a floppy disk. Thus, it's recommended to wait for the desktop to appear until a second floppy can be inserted. Before loading a different disk image, it's recommended to eject the previously inserted disk image from within the OS.

Note that the floppy disk drive will not be read when the CPU speed is set to 16 MHz.

Official system disk images are available from an archived Apple support page here. Under Linux these can be converted into the desired dsk format using Linux StuffIt, unar, and dc2dsk, in that order. A shell script has been provided for convenience at releases/bin2dsk.sh.

Hard disk support

The MacPlus core supports SCSI hard drive images up to 2GB (HFS) in size, with a .vhd extension. The core currently implements only a subset of the SCSI commands. This is sufficient to read and write the disk, to boot from it, and to format it using the setup tools that come with System 6.0.8.

The harddisk image to be used can be selected from the "Mount *.vhd" entry in the on-screen-display. Copy the boot.vhd to MacPlus folder and it will be automatically mounted at start. The format of the disk image is the same as the one used by the SCSI2SD project, documented here.

Unlike the floppy, the SCSI disk is writable and data can be written to the disk from within the core.

It has been tested that System 6.0.8 can format the SCSI disk, as well as doing a full installation from floppy disk to the harddisk. However, keep in mind the core is an early work in progress and expect data loss when working with HDD images.

A matching harddisk image file can be found here. This is a 20MB harddisk image with correct partitioning information and a basic SCSI driver installed. The data partition itself is empty and unformatted. After booting the Mac will thus ask whether the disk is to be initialized. Saying yes and giving the disk a name will result in a usable file system. You don't need to use the Setup tool to format this disk as it is already formatted, but you can format it if you want to. This has only been tested with System 6.0.8.

A tool to create harddisk images (with working SCSI driver and partition table) is available here.

CPU Speed

The CPU speed can be adjusted to 8 MHz (original speed) or 16 MHz. This port implements a workaround to allow booting from SCSI when using the 16 MHz configuration.

Memory

1MB and 4MB memory configurations are available. Cold boot with 4MB RAM selected takes some time before it starts to boot from FDD/SCSI, so be patient. Warm boot won't take as long.

Keyboard

The Alt key is mapped to the Mac's Command (⌘) key, and the Windows key is mapped to the Mac's Option (⌥) key. Core emulates keyboard with numeric keypad.