512k/Plus Hard Drive

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Last seen: 8 years 1 month ago
Joined: Mar 12 2005 - 13:18
512k/Plus Hard Drive

So, there's an HD-20 that can be used on the floppy port of both a 512k and a Plus. I'm guessing if I wanted to, I could use a ribbon cable and attach it to the internal drive connector assuming I had the 128k ROMs installed.

So I got to thinking ... the HD-20 is too big to fit the parts into the case and it would certainly use too much power and create too much heat. BUT, what if I could fit a 2.5" powerbook SCSI HD inside the case?

Basically, I've already done this in my Color Classic with a 2.5" to 3.5" adapter. I think it would be a no-brainer with an SE as it has an internal SCSI connector. A Plus is a little more complicated as it only has an external SCSI connector and a 512k has no SCSI connector without a hard-to-find add on board (though if I found one, I could use the connector inside the Mac's case).

Here's the rub -- I want to use the 512k case, so even if I could modify the Plus logic board to add an internal SCSI connector, it wouldn't fit in the 512k case. CAN an internal SCSI connector be added to the Plus by just tapping into the logic board somehow? The easiest thing to do would be to find a SCSI expansion kit -- anybody got any ideas about that or any experience? Will a Mac 512k boot from a SCSI drive connected to these expansion kits?

NOW FOR THE CHALLENGE HACK -- the 512k will use a HD-20. There is plenty of room in a 512k for the HD-20 controller board to plug into the internal drive connector and a 2.5" SCSI hard drive -- not to mention the smaller drive puts off very little heat. I've always heard the HD-20 is basically a Rodime SCSI drive and that there were conversion kits that simply required bypassing the Apple controller with a new circuit board and turned your HD-20 into a SCSI drive. Seems to me the 2.5" SCSI drive could likewise be adapted to use the HD20 controller. Anybody got any ideas how I would go about it?

The HD20 has a 26-pin connector to the controller board. This seems a lot like a DB-25 SCSI connector. If I had a pin-out, it might be a simple matter of building a converter from the 26-pin connector to the 2.5" drive connector.

dankephoto's picture
Last seen: 9 months 1 week ago
Joined: Dec 20 2003 - 10:38
use a Plus board and . . .

internally tap the external scsi connector for the signal. Eazy-peazy! Right? Biggrin

Dunno 'bout the HD20 bizness though, that thing runs off the bloody floppy port, slow as all getout. And do you have any actual knowledge about the HD20's mechanism being SCSI? I'm clueless BTW, only ever took my HD20 apart once (just for funzies) and that was long ago and I remember nada 'bout the interface details.

Really, if you just want that nice silent classic Mac, then a Plus is definitely the way to go.

dan k

Last seen: 8 years 1 month ago
Joined: Mar 12 2005 - 13:18
Apple HD-20: How To Convert It Into A SCSI Device


There is a product that converts an Apple HD-20 into an SCSI device. Available
from Personal Computer Peripherals Corporation, it is called HD-20 WSI.

The HD-20 WSI is an upgrade for the original Macintosh HD-20 that allows it
to interface with the Macintosh Plus, Macintosh SE, and Macintosh II via the
SCSI port. The HD-20 WSI modification provides users with significantly faster
access to the data stored on the hard disk.

The modification consists of a plug-in circuit board, interface cable, and
utility software. The circuit board uses the existing HD-20 connectors and
requires no soldering. The utility software includes HFS Backup, Eureka (a file
finding application), a floppy disk copy program, and ImageWriter/LaserWriter

For more information, search under: "Personal Computer Peripherals"

Last seen: 2 years 2 months ago
Joined: Dec 20 2003 - 10:38
Dove SCSI expansion

The most elegant solution would be to use a Dove MacSnap kit on a 512K motherboard and 128KB ROMS. This would provide you with RAM expansion and a SCSI bus. It would be relatively easy to mount a low power SCSI drive inside the Mac and layout the ribbon cable to provide an external SCSI bus.

Dove MacSnap info:

As far as adapting an HD20 for use internally, it sounds a no-goer. The Rodime mechanism is unlikely to be compatible with SCSI because it predates publication of the SCSI standard by two years...


Last seen: 8 years 1 month ago
Joined: Mar 12 2005 - 13:18
Tend To Agree

Yup ... Now I'll just have to start my ebay vigil to find a MacSnap! There were several other cards as well (SC II by Sophisticated Circuits, Mac's-a-million, etc.). Doubt I'd use the memory upgrade part as it would only tax the internal heat and analogue board. Did not realize that the Rodime predated the SCSI standard. Guess the SCSI adapter kits were really a converter and would probably need something similar to go from SCSI to floppy and I'd have to build it since I'm sure there wasn't much of a demand for such a retrograde! I did come across a step-by-step to mount a HD inside a compact Mac: http://www.users.qwest.net/~jgarbacz/512k.html I can only imagine you could have used it to smelt the metal from itself after running for a few. But, makes me realize there is plenty of room to put the HD-20 in the case if I were a masochist. I must add that I find hard drives as noisy as fans and for all of Steve Jobs ranting about fans, the HDs are just as big a problem if not bigger. And the older ones cannot be put to sleep. In fact I read that the original Apple ProFile hard drive manual recommended that you NEVER turn it off! But I figure a PowerBook HD would be the decent compromise. I could probably even mount it inside a sound deadening case. Thanks for the info!

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