Support of the serial HD-20s is not tied to System Software, but to the ROM
in the respective systems.
The following Macintosh models have support for the serial (non-SCSI) HD-20
built into ROM:
- Macintosh 512K (with hard disk 20 Patch)
- Macintosh 512Ke
- Macintosh Plus
- Macintosh SE
- Macintosh SE/30 (not supported with original ROM, but it is supported with ROM-inator II or other ROM upgrade)
- Macintosh Classic
- Macintosh Classic II
- Macintosh IIx (not supported with original ROM, but it is supported with ROM-inator II or other ROM upgrade, connects to the second internal floppy header)
- Macintosh IIcx (not supported with original ROM, but it is supported with ROM-inator II or other ROM upgrade)
- Macintosh IIci
- Macintosh IIvi (connect to SWIM PLCC Pin 19)
- Macintosh IIvx (connect to SWIM PLCC Pin 19)
- Macintosh IIsi
- Macintosh LC (second internal floppy header)
- Macintosh LC II (connect to SWIM PLCC Pin 19)
- Macintosh Portable
- Macintosh PowerBook 100 (with adapter)
The following Macintosh models do NOT have this support built in:
Macintosh SE/30- Macintosh II
Macintosh IIxMacintosh IIcxMacintosh IIsi- Macintosh IIfx
Macintosh LC
For more information on the serial HD-20, see the article "Old HD20 and New
Mac SE/30".