This article is from the Apple II Csa2 FAQ, by Jeff Hurlburt with numerous contributions by others.
Mac--> IIgs Yes. However, Macs put a driver on the disk as well as a partition map. Both look like partitions to the IIgs. Since the IIgs can't read them, it will ask you to format or eject. Here's a trick you can try: When you insert a Mac- formatted Zip, just click "eject" until the disk mounts. The IIgs will then ignore the extra Mac stuff, and mount just the legitimate volume(s). (E. D.) ---------------------------- By: Supertimer Mac <--> IIgs Shared HFS GS/Mac disks should be formatted on the IIGS because the IIGS tends to provide a format that is acceptable to both platforms while the Mac tends to ignore the needs of the IIGS. Besides the standard Apple Disk Utility (ADU), you will need GenEx. GenEx extracts the generic Mac SCSI driver from ADU's resource fork and puts it into the IIGS' drivers folder. Thus, when ADU looks in that folder, it finds and installs the driver and does not give the "no mac driver found" error. You can download GenEx (GenEx.shk) and info (GenEx.shk.txt) from Ground at ... ftp://ground.ecn.uiowa.edu/apple2/upl98/Feb98/ . Once you get GenEx, use the following procedure to prepare Zip disks: o- Go to the Apple Advanced Disk Utility (ADU) on the IIgs and select Partition Drive. Delete all the partitions except one and resize that one partition to fill up the entire drive. Click on the button to repartition the drive. At this point, ADU will ask you if you want to low level format and warn you that it is going to take a long time. Click on Yes. o- ADU will wipe the drive. By doing it this way, you are giving ADU a clean slate to install the GenericMacSCSI driver onto the drive. o- Finally, initialize the HFS volume. Surprise, the new Zip disk works on both the IIGS and Mac without annoying errors! ---------------------------- By: John Holmes and Tarage PC--> IIgs (also, maybe, IIgs--> PC and PC <--> Mac) DataViz sells a product called MacOpener 2000 for machines running Windows that actually allows you to use all HFS formats, except for 400K/800K floppies, on your PC while running Windows. This goes not only for reading the media but also writing and formatting as well. I put a zip disk in my Parallel Port Zip drive on my PC and formatted it HFS and copied some of the //gs software I had downloaded. It worked on my IIgs (equipped with a SCSI zip 250 drive) like a charm! ---------------------------- By: Supertimer and Rubywand PC<-->IIgs You can use MUG! to R/W MS-DOS formatted Zip disks. Mug! (mug101.bxy) along with an info file is on Ground at ... ftp://ground.ecn.uiowa.edu/apple2/apple16/System/Ndas/ . MUG! is an NDA (New Desk Accessory) which must be started from the 'Apple menu' (click on the Apple symbol) available at the top of a typical GS 'desktop'-type display. One thing to be aware of is that MUG! should be used from an application other than Finder (the usual main GS "desktop display"). The Finder and many other applications will do a drive check, find the MS-DOS Zip disk, and respond with something like: "Installed FSTs do not recognize disk, do you wish to format it or eject it?". MUG! seems to work fine when selected from Platinum Paint or PMPUnZip. (If you start from Platinum Paint, be sure to go to 640 mode first in order to be able to see the entire MUG! display.) PMPUnZip is, probably, your best bet because it is a relatively small program. Once, say, PMPUnZip is started, you can insert your PC Zip MS-DOS Zip disk and start MUG!. Setting the Copy option to "to GS/OS", I copied several .shk, .wav, and .jpg files from the Zip Disk to /RAM5 RAM disk with no problem. By: Rubywand