JDW wrote:Mac128 and Gorgonops, thank you for the interesting discussion on IDE. However, as I have repeatedly said throughout this thread to everyone who has brought up that ST-506 drive, the drive mechanism used in my HyperDrive Mac512 is NOT an ST-506.
In case you missed the distinction (which was made several times over in this thread) in the thread posts mentioning "ST-506" we are referring to the details of the interface protocols and cabling, we are not talking about the drive mechanism. The "ST-506" interface (also called ST-412, based on the model of the 10MB hard drive used in the original IBM XT which used compatible cabling and controllers) was an ad-hoc industry standard and *many* different manufacturers made many different models of compatible drives.
To make it more clear:
The wikipedia article. Note the section detailing "compatible systems and developments.
The PCguide.com entry on the interface.
And for more references, just go to Google and search for "ST-506 Interface".
Further, looking at your pictures of the Hyperdrive controller I see onboard a chip labeled "WD-1010-PL". Here is a link where you can download the datasheet for the WD1010 controller chip. On the first page the first line under the "FEATURES" heading is a bullet point that says "ST506-SA1000 COMPATIBLE". (The SA1000 is a slightly earlier 8" form factor drive compatible with the ST-506.) So... no matter who made the particular drive mechanism in your system, I'd say the evidence is pretty overwhelming that it is an "ST-506" drive.
According to a list of "defunct hard drive manufacturers" MMI "left the industry", and it's pretty apparent they did so without a trace. (Googling enough turned up another reference to them in a presentation slide deck talking about consolidation in the hard drive industry.) Making knockoff ST-506-style hard drives used to be something that could be done in a small garage machine shop, and California used to be crawling with little companies doing just that, some of which died quietly and others which ended up imploding in a spectacular fashion. (MMI seems to have been in the "whimper" category.) I would bet you a shiny new nickel that there's absolutely nothing special about the drive, so if it's broken I'm sure you could replace it with one from another manufacturer assuming you can find one that has a suitable geometry. (If the formatter program doesn't let you specify the size and geometry of the drive a replacement would need to have *at least* as many heads and cylinders as the original. A larger one would work if wasting some of it would be acceptable. I would suggest a possible source being the 3 1/2 hard drives used in PC "hardcards" in the mid-80s, although those aren't exactly easy to find in working condition anymore.)