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How to test Apple HD20 without a Mac Plus or 512k?

Posted by: wilykat on 2014-10-01 02:14:29 My Mac Plus is stored at my parent's place and I don't have any plan to make a 400-ish miles trip just to get the Mac Plus. I did find the 20MB hard drive with the disk drive cable.  Currently I have a Powerbook Duo 280 and floppy dock which takes a square powerbook style connector, a Wallstreet and iMac with no disk drive, and a Centris 610 with only internal disk drive.  System 7.1 is the lowest System I have, other being 7.6 and OS 9.2 Can I jury-rig an adapter and connect the hard drive to my Centris' internal disk drive port? Or did Apple leave the support out?  Any way to test it beside plugging the power in and checking for smoke?

Posted by: Mk.558 on 2014-10-01 06:17:39 No. 512K, 512Ke, Plus, and SE. SE FDHD (1.44MB drive upgrade) I'm not sure about. There was discussion about a strange INIT for the SE/30, but nobody has it anywhere. The Mac II is still up on the air: I seem to recall something about the HD20 with the Mac II. You'd probably need some kind of NuBUS card because the Mac II doesn't have a floppy drive port, or hack some kind of weird thing which hooks into one of the floppy connectors on the motherboard. IFAIK the Classic II was the last one to have a port on the back for an external FDD. Even if you could plug it in, the ROMs won't have support for the HD20 in the first place.

Posted by: olePigeon on 2014-10-01 10:06:06 I bet you could get it to work with a Macintosh II series computer if you added support for it in a Dougg3 ROM. Seems like a worthwhile thing to try if it hasn't been attempted already.

Posted by: max1zzz on 2014-10-01 11:25:41 I remember reading that there is some init for the IIfx to use a HD20 (you had to take it apart and connect it directly to the logicboard) Cant for the life of me remember where though... I wouldn't try connecting it to a unsupported mac. i do remember the guide for using one with the IIfx essentially said "it's a bad idea and may void your warrenty, but will let you get your data"

Posted by: wilykat on 2014-10-01 12:18:12 Guess I'll wait to get my Plus out of retirement.

Posted by: ScutBoy on 2014-10-03 06:13:49 Here's the info from Apple's support page. http://support.apple.com/kb/TA40360?viewlocale=en_US 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 512Ke * Macintosh Plus * Macintosh SE * Macintosh Classic * Macintosh IIci * Macintosh Portable The following Macintosh models do NOT have this support built in: * Macintosh SE/30 * Macintosh II * Macintosh IIx * Macintosh IIcx * Macintosh IIsi * Macintosh IIfx * Macintosh LC

Posted by: Elfen on 2014-10-03 08:29:49 That is an interesting list. Why would the IIci have such support for the HD20 and the IIcx does not when the IIcx came before the IIci? Some answers may never be known.

Posted by: olePigeon on 2014-10-03 08:36:03 Oh.  Weird.  So if you pop a IIci ROM into a IIcx, it should work, correct?  Sounds like the perfect job for a Dougg3 ROM. 🙂

Posted by: unity on 2014-10-03 09:04:29 here was an interesting link on the HD20 and the FloppyEMU and the use of a dougg3 rom. https://68kmla.org/forums/index.php?/topic/21368-floppy-emu-emulating-hd20/

Posted by: olePigeon on 2014-10-03 09:17:43 So, begs the question if the Macintosh SE/30, IIcx, and IIsi have a buffered floppy port.  If they do, then you could reasonable swap a IIci ROM into an SE/30, IIcx, or IIsi (via Dougg3 ROM) and use the HD20.

Posted by: slomacuser on 2014-10-03 09:45:27 Recently I bought another HD20 and tried to initialize it with Macintosh SE and it froze the SE or give me error message no mather how much I tried and tried with diferent System Software versions. I tought, oh no another dead HD20 I have no luck, anyway I then conected it to the Mac Plus to see if the drive is really bad but it worked immediately ... From now on I would not try to test or initialize HD20 on other Mac than Plus

Posted by: olePigeon on 2014-10-03 12:00:49 Those HD20 sure do look sexy next to a 128/5128/Plus, though. Can they be daisy chained?

Posted by: slomacuser on 2014-10-03 13:29:02 Two for sure, I do not know if 3 or more would go too

Posted by: Paralel on 2014-10-03 15:37:25 I wish someone would continue with trying to make an HD20 emulator. Not having a second cord for the plus sure would be nice.

Posted by: rsolberg on 2014-10-03 18:16:21 Hey Paralel, what about a power Y-cable with two IEC C13 plugs on the end? I was contemplating fabricating something for my CC and external drives, but noticed they're commercially available.

Posted by: Paralel on 2014-10-04 12:34:53 I don't see why that wouldn't work. I like it. If you give it a try, let me know, that might just solve the problem.

Posted by: olePigeon on 2014-10-04 23:48:45 According to Wikipedia, the maximum number of floppy drives that can be accessed at one time is 3.  I don't know if that limitation applies to external floppies or an HD20.

Posted by: Byrd on 2014-10-05 05:00:02 I might be wrong, but does it have something to do with the interleaving compared with Plus and SE Macs (yes I know the HD20 is not SCSI).

Posted by: uniserver on 2014-10-05 12:03:25 i hear ya  Paralel Yeah a HD20 emu would be super awesome!  Would be great to use with all the scsi-less compacts. BMOW's final word on this project was,  "its been moved to the back burner"  so that is slightly promising. maybe he will get some spare time this winter and make some progress with it.

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