Macintosh Hard Disk 20

[uniserver]

! have great news… the se/30 boots from the HD20, with Dougg3's ROM simm installed!

 

[uniserver]

lol i have great news IIcx boots the HD20 with dougg3's rom simm installed.

 

[uniserver]

my hunch is the IIx and IIfx would also boot hd20 with dougg3's rom simm!

obviously it would have to be hooked to the internal floppy connector… no big deal… i have a 2 foot floppy cable hanging out of my MacII for the Floppy Emu already.

as soon as i get my package from olepigeon, I'm going to try and solder a rom simm slot onto the Mac II.. and try dougg3's rom.. i am almost positive it will work.

now all we need is to get a BMOW Floppy Emu … to Emu a HD20 !!

 

[uniserver]

Using the HD20 hard drive… I would say its speed is similar to Booting your computer up and running it with an IOMEGA SCSI Zip 100.

I don't find it to be abnormally slow at all… that IWM is working its magic!!!!!

maybe even black magic!

 

[Gorgonops]

Using the HD20 hard drive… I would say its speed is similar to Booting your computer up and running it with an IOMEGA SCSI Zip 100.I don't find it to be abnormally slow at all… that IWM is working its magic!!!!!

maybe even black magic!

It transfers data at effectively 7/8ths * 500kb/s, IE, around 55K/sec. In *theory* the SCSI version of the original ZIP 100 should be capable of bursting around a megabyte a second but the SCSI hardware/driver implementation in early Macs like the Plus is so horrible that the 55K/s from the HD20 is, well, almost in the same ballpark. (A Plus falling downhill with a tailwind can eek around 200-250K/s with a sufficiently fast drive.) If you're running System 6-era programs they're going to be small enough that the speed is going to be "adequate".

For any Mac that *does* have a SCSI port it makes a lot more sense to fit a SCSI->Flash adapter for "production" use; it'll be faster and more likely to be bootable. That said, I'm totally rooting for BMoW or others to reverse engineer HD-20 emulation anyway for use with 512k(e)'s and friends, and there certainly might be some edge cases where it could be useful for data transfer purposes when attaching the device to a newer Mac.

If I had to hazard a guess as to when support for the HD-20 it was pulled completely it's the cutoff between models using the SWIM chip and the SWIM II. See this "what chips are in what Macs" list here. The HD-20 support is in the floppy driver and the SWIM II's drivers are completely different from the SWIM's. (Which means the HD-20 init definitely won't work to add it.) So if you really, really wanted to probe the edges of support you could try cooking up an adaptor from the internal floppy connector to external and hooking the HD-20 up to an LCIII or Quadra (later than the 700 and 900). Pretty sure you'll hit the wall there.