ALERT: eBay Auction, Hyperdrive 512k in Disguise!

An individual who used to be a GCC HyperDrive dealer in the 80's contacted me recently and we've had a long discussion about our respective units. He inspired me to take shoot additional photos of my MMI MM 112 drive mechanism, which I recently posted here:

https://picasaweb.google.com/103365672326265854011/GCCHyperDrive20DriveMechanism#

He also sent me the following scan which reveals some data about my MMI drive:

https://docs.google.com/open?id=0B3mQLg8d1xThNmI1YjExOTYtY2Y3OS00MTA4LWEyNjUtYzk5YWNkMGUzM2Y1

And this web page indicates my MMI drive has an ST-412 controller, which if true is the newer variant of the ST-506 interface:

http://protovision.textfiles.com/computers/hd_ref41.lan

So it seems I have a 10MB, not a 20MB drive after all. He also said my Hyperdrive is an early model unit and not one he was familiar with, especially because latter Hyperdrive models didn't have MMI drive mechanisms in them (to his knowledge). There must not have been many of these made, because I've been unable to find a photo of one that exactly matches the shape of my drive (although most ST-506 drives are quite similar). In any case, I am very pleased with this info, which sheds more light into the history of my drive mechanism. I hope you reading this find it informative as well.

Thanks for posting those pictures. Now there IS documentation of an MMI mechanism available. I guess I should post pictures of my old disk drives for reference too. That big list covers some short-lived drive manufacturers, even a couple who never reached production. Different from today with only Seagate and WD in the same flooded industrial park...

JDW, I like your "Apple within an apple" avatar. Especially on a cube.

I suppose this is useless trivia, but according to the platter/head/cylinder layout (2/4/306) that MMI drive in your Hyperdrive is from a logical standpoint literally a shrunken clone of the Seagate (Shugart) ST-412, the full-height 5 1/4" drive used in the IBM 5160 XT. (and namesake of the "ST-412" nomenclature denoting ST-506 drives which support buffered seek requests.) Space issues aside if you had an XT sitting around you could literally uncable the drives from both machines, swap them, and format them to full capacity on each other's controllers using the stock settings.

(It's probably sad that I didn't have to look up the Seagate settings. I had them memorized from having an ST-412 as my first hard drive.)

Basically what this translates to is almost *any* MFM (or RLL, they're the same hardware, just the data encoding method differs) hard drive with four or more heads and of suitable physical size would work as a replacement for a bum Hyperdrive. Drives with fewer than 306 cylinders are pretty rare. (Of course, if the formatting software lets you specify the size/geometry than you could use basically any drive that fits.)

...almost *any* MFM (or RLL, they're the same hardware, just the data encoding method differs) hard drive with four or more heads and of suitable physical size would work as a replacement for a bum Hyperdrive.

Click to expand...

Although my MMI drive still works, I would prefer to replace it with a flash drive, since any replacement spinning platter drive that was made back in the early 1980's would have the same potential for failure, not to mention high current consumption, slow speed, noise, etc. However, I am not aware of any MFM or RLL drive replacement flash solution. Are you?

There actually are a couple commercial solutions for replacing MFM/RLL hard drives with either SATA or flash... but they are turn-your-hair-white expensive, unfortunately. (North of $2000.)

Its something still just a little out of the "easy homebrew" ballpark, alas. It would probably be doable with an FPGA but it requires handling serial data at about 20mhz with no latency. (Or to put it another way, it's about ten times harder than a floppy emulator.)

I found an exact flash replacement for my MMI M112 drive:

http://www.datexdsm.com/disc/disque33.html

But the price is not shown, which leads me to believe it may be as costly as you suggest, Gorgonops! I'm afraid to even ask them about the price!

UPDATE: I just found out the price. Sheesh:

http://datex-boutique.com/product.php?id_product=47

Yeah, the emulator products are priced so they might make sense if you desperately need to keep some dedicated industrial computer running. (You'll find MFM or RLL hard disks floating around in the strangest places, up to and including aircraft avionics systems.) For a hobbyist? Not so much.

I know it's a long shot, but... do any of the contacts you've found that used to work on the GCC Hyperdrive have access to the source code for the drivers and ROMs? Far more practical at a hobbyist level than creating an MFM hard drive emulator (where you have to deal with high speed serial data streams with no flow control) would be creating a complete "Hyperdrive Substitute" consisting of a Compact Flash/PATA IDE port on a 68k socket daughter card. The hardware is trivial. (Homebrew devices like that are a dime a dozen in the Atari ST and Amiga fields.) Writing drivers for custom devices is always the hard part for the antique Mac community. Since IDE/Compact Flash drives actually (partially) emulate the programming interface of a Western Digital ST-506 controller chip having the source for the Hyperdrive drivers would give you an easy leg up for writing a driver for an Atari ST-style parasite IDE board. A good programmer could probably adapt them in a few hours.

The easy way to put a hard disk emulator in a Mac 512 is to add one of the SCSI-equipped upgrades and Mac Plus ROMs. From there, add a notebook SCSI drive like I have in mine, or use a SCSI-IDE adapter and a CF card or something like that. You can even beef up the analog board enough to run the drive without an added power supply. No hacking assembly language required.

http://web.me.com/henryspragens/stuff/Photos/Pages/Computers.html#10

It wouldn't be a HyperDrive, though, or use any of the HyperDrive parts. If you need HyperDrive source code, you probably will have to disassemble your ROMs and create your own, like we did with the Mac 128K ROMs to run our disk drives in 1984. A solid-state HyperDrive will either be very expensive or a lot of hacking.

A solid-state HyperDrive will either be very expensive or a lot of hacking.

Click to expand...

A typical Atari ST IDE board (which would be the same hardware, essentially) is four (or less) ICs on a few square inches of double-sided circuit board. That's not exactly expensive considering the price of SCSI-IDE bridges. It is, however, a lot of a hacking.

(If you're willing to replace the stock Mac ROM with EPROMs containing a hacked version my guess would be the simplest way to do a driver from scratch would be to start with the Mac Plus ROMs and replace the SCSI driver with your IDE drive code. The only thing the Hyperdrive source would give you is some hints on how to make the whole lashup work with the 64k ROMs. Hyperdrives worked with those, right?)

I just added 11 new HyperDrive photos today:

https://picasaweb.google.com/103365672326265854011/GCCHyperDrive20DriveMechanism

Be sure to read the commentary beneath each photo, and click the little magnifier to zoom in more. As you can see, it clips to a stock Mac 512k logic board with the original 64k ROMs.

I've just posted another 720p video here that shows the HyperDrive Mac 512 booting to the Desktop:


I also shot it from the side while booting, with the case back off.

nice drawer icons, can you copy them and put them online?