Richard Crispin writes: > > Apple II ProDOS 3.5" disks are usable in the Macs floppy drive. I > don't know if the 5.25" drive will work. The floppy drive port has changed quite a bit over the years. The details below come TechInfo articles from Apple's web site: http://til.info.apple.com/tilarchive.nsf/artnum/n206 http://til.info.apple.com/tilarchive.nsf/artnum/n1424 http://til.info.apple.com/tilarchive.nsf/artnum/n2396 http://til.info.apple.com/tilarchive.nsf/artnum/n3798 http://til.info.apple.com/tilarchive.nsf/artnum/n8014 http://til.info.apple.com/tilarchive.nsf/artnum/n12923 http://til.info.apple.com/tilarchive.nsf/artnum/n12924 http://til.info.apple.com/tilarchive.nsf/artnum/n12933 http://til.info.apple.com/tilarchive.nsf/artnum/n12934 http://til.info.apple.com/tilarchive.nsf/artnum/n12943 http://til.info.apple.com/tilarchive.nsf/artnum/n12944 http://til.info.apple.com/tilarchive.nsf/artnum/n12947 Here's the Disk-II pinout (used by the first Apple II floppies; pin signal pin signal --- ------ --- ------- 1 GND 2 SEEKPH0 3 GND 4 SEEKPH1 5 GND 6 SEEKPH2 7 GND 8 SEEKPH3 9 -12v 10 WRREQ 11 +5v 12 +5v 13 +12v 14 ENBL 15 +12v 16 RDDATA 17 +12v 18 WRDATA 19 +12v 20 WRPROT where: SEEKPH0-3 directly controls the four magnets in the stepper motor that controls head position WRREQ is write-request ENBL enables the drive (turns the motor on) RDDATA is read-data WRDATA is write-data WRPROT is write-protect The //c port carries (mostly) the same signals, but the pins are numbered differently - which is fine because the connector changed. (The Disk-II used a 20pin header, while the IIc drive port uses a DB-19 connector). The big difference in the signalling is that DR2 is added to select which of two possible drives should be active) pin signal pin signal pin signal --- ------ --- ------- --- ------- 1 GND 8 +12v 15 WRREQ 2 GND 9 ENBL 16 --NC-- 3 GND 10 WRPROT 17 DR2 4 GND 11 SEEKPH0 18 RDDATA 5 -12v 12 SEEKPH1 19 WRDATA 6 +5v 13 SEEKPH2 7 +12v 14 SEEKPH3 where: WRREQ is write-request --NC-- is no connection DR2 selects drive 1 or 2 The IIc+ modified these signals a little, in order to support the 3.5" drives. An ID pin was added to identify the drive type, an extra drive-select was added (replacing ENBL) to allow up to four drives, and a head-select was added to allow double-sided drives. But overall, the pinouts remain compatible with the Disk-II and IIc interfaces. pin signal pin signal pin signal --- ------ --- ------- --- ------- 1 GND 8 +12v 15 WRREQ 2 GND 9 DR2 16 HDSEL 3 GND 10 WRPROT 17 DR1 4 3.5DISK 11 SEEKPH0 18 RDDATA 5 -12v 12 SEEKPH1 19 WRDATA 6 +5v 13 SEEKPH2 7 +12v 14 SEEKPH3 where: 3.5DISK identifies the drive as a 3.5" disk or a 5.25" disk DR1 is used to select the drive, along with DR2 HDSEL selects the drive head When the Mac comes out, however, a lot of these signals change. They have to, since the port can now support hard drives. I think the drive port on the IIgs also uses this pinout (but I couldn't find a document about the GS's port). pin signal pin signal pin signal --- ------ --- ------- --- ------- 1 GND 8 +12v 15 WRREQ 2 GND 9 --NC-- 16 SEL 3 GND 10 PWM 17 ENBL 4 GND 11 CA0 18 RDDATA 5 -12v 12 CA1 19 WRDATA 6 +5v 13 CA2 7 +12v 14 LSTRB where: PWM controls the drive motor speed. CA0-CA2, LSTRB and SEL are control lines, used for sending commands to the drive. These differences are why a Mac 3.5" disk won't work on an Apple IIc, without a proprietary interface card in it. (The UniDisk drives came with this card in them.) Also note that some later models of Mac changed pin 10 to no-connection. So, in short, no. An Apple-II floppy drive can no be plugged directly into the drive port of a Mac. And a Mac-compatible drive can not be plugged into the drive port of an Apple IIc, even though the same shape connector is used. (The one exception, again, being the UniDisk 3.5, which has an interface board to make it compatible with both the IIc and Macs.) -- David