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Mystery Hardware (what is it?)


Well-known member
Hi guys. I have here an expansion card. From what I can make out it has an Interface Controller of some sort and a bunch of discrete logic. I'm guessing homebrew or hobbyist kit by the solder job, the latter most likely by the lettering on the component side done in tinned copper ...

The cable is 34-pin IDC Ribbon, just like on a PC floppy drive, leading me to speculate it may be designed to drive a PC floppy drive.

I would be interested to know if I can make it work in my IIgs - and what it is.

Pics follow:







Well-known member
Bets are good that if there's isn't a definite company logo or name and version number somewhere, it's probably the work of a hobbyist, someone with nice tools and equipment, maybe a kit maker as you suggested. There's a bunch of easily identifiable integrated circuits and they are:

MC68B21P - Peripheral Interface Adapter

HM6116LP-3 - 16K SRAM

NEC D2716D - 16K EPROM

74LS00 - NAND Gate (Logic)

74LS08 - AND Gate (Logic)

SN74LS38N (4) - NAND Buffer (Logic?)

74LS244 PC - Octal Driver Tri-State

74LS245 PC (2) - Octal Bus Transceiver Tri-State

74???? PC (1) - Not sure, seems to have lost it's markings to time (or a dark photo location)


So, I think it's completely reasonable to consider an interface card, given the info. It would seem that it is an 8-bit interface since it uses an octal driver and transceiver. The fact that it has a transceiver suggests that it does input and output, not just one or the other. I would guess that it has firmware of some kind (given the EPROM), so it's not completely done in hardware. If it came with that cable it's probably not a Serial/Parallel card (can't say for certain) which means it's most likely not an input only device or a communications card. That said, I'd bet on some kind of storage interface, probably a floppy or hard drive interface. Although it maybe difficult to tell without testing.

If you're fairly sure it's for one of the Apple II series, you should get some specs on the Apple II bus and the circuitry. Then you should do some mental tracing backwards and get an idea of which connectors on the header go to positive voltage, ground, and data lines. Make sure that the circuitry (the ICs present) is actually rated for the Apple II bus interface voltages. If the results of a thorough examination line up with the Apple II bus specs, you can try plugging it in and see what happens. Even if it does connect to a PC floppy drive (which might be hard to say for certain), it probably won't work right away unless it acts like the Disk II controller, but interfaces to a different kind of drive. You'd probably need software. If you end up connecting the card and don't have a definite result, you can try measuring the lines on the IDC connector and compile data on the signals (an oscilloscope would be more useful, but multimeter measured analog signals might be sufficient in this case). In any case, if it's a floppy card for a standard PC drive (not an old one that comes with an enclosure), it probably won't provide power to the drive. That said, you'll need a powered drive to test that theory.

Best of luck with your interesting looking card.


Betting those blue ceramic capacitors are on the voltage supply line.



Well-known member
I would say it's def. for an Apple II due to the fact that the only text (except for the upper left corner) on the board is an "A II" along the lower edge.



Well-known member
I agree that it's likely to be a floppy drive controller.

The 74LS38 devices use open-collector logic, as do PC floppy drives. There are what appear to be pullup resistors adjacent to the 34 way connector and the 34 way cable has a connector for a second device half way along it in the same fashion that floppy drive cables are set up. However, this last observation may simply mean that the cable is off a PC floppy drive, while the card was intended for something else.

The mystery is; if it is a floppy controller, then where is the PLL and all the associated "analog" stuff? The Apple II floppy controller cards were unique in that they used some very clever Woz logic to do away with all the traditional complexity of a disk controller. I've never seen anyone else emulate this.



Well-known member
Is there any more text under the blue capacitor at the bottom? A][ ????? What does it say at the top? Are there any hidden letters? That might hint at Apple ][ (what). It's a dual port parallel interface to something, perhaps a printer, depending on the firmware. What happens when you address it, ie put it in a slot and type "PR#(slot)" and "IN#(slot)"? You may have to disassemble the ROM code to figure out what it's for. It doesn't seem likely to be for a floppy unless the floppy has onboard intelligence. It might be for an IDE HD, but then the cable would probably be 40 pins. If SCSI, it would have 50 pins. 6821s were often used for printer interface cards. The RAM would be for buffering text so the printer could work while the Apple went about another task.



Well-known member
Shred has almost convinced me that this is an MFM floppy disk controller. If so, which disks?

Edit: MFM requires less logic than GCR.



Well-known member
If it's a floppy controller for Apple II, then 5.25" or 3.5" floppies. Probably SS-SD/DS-DD, NOT High Density most likely.



Staff member
I personally doubt it's a floppy controller, as the parts list seems wrong. Why would a floppy controller have a RAM chip on it unless it also had a microcontroller, which this lacks? And if it were a controller designed to drive MFM floppies wouldn't it be logical for it to incorporate an FDC controller chip? It doesn't look to me as if there's enough discrete logic on that board to run a floppy drive otherwise. (There's no UART so it'd have to "bit-bang" the data stream, which I guess might be possible given that's essentially what the Disk ][ controller does, but then what's the RAM chip for again?) The use of a 34 pin ribbon cable doesn't really shed any light on the subject, as it was a terribly common connector. (TRS-80s, for instance, have identical looking 34 pin card edge connectors for parallel printers and disk drives. You had to know which port was which.)

Here's a link to an MFM controller card for Apple IIs. Note the use of an FDC chip, in this case an Intel 82077

The card makes more sense interpreted as a parallel I/O port, but not necessarily for a printer. As to exactly *what* went on the other end of that cable... perhaps examining the contents of the onboard ROM would provide some hits.



Well-known member
cannot see the photos, but from chip list it sounds a bit like a profile HDD controler...



Well-known member
The pic doesn't look the least bit like an Apple II or Apple III Profile card. Also, the Profile doesn't have either a MC68B21P or a HM6116LP