Dali Clock: further adventures in retrocomputing

So, for those of you tuning in late, back in 1991 I wrote this program called XDaliClock, which is a clone of a similar program that I had on my Mac in 1984. I sold that machine in like, 1987, and I'd been halfheartedly trying to find another ever since, because I wanted a machine that was still capable of running the original Dali Clock. Well, back in April, cyantist bought me one! And tonight, I finally got around to getting the original Dali Clock running on it. That means that I now have a dedicated Dali Clock Appliance, made of the absolute wimpiest computer capable of generating that effect.

Even the original Palm Pilot (on which XDaliClock also runs) is a way beefier computer that the original Macintosh is: the screens are almost the same resolution, but the Pilot's CPU is at least 4x faster (maybe more?) and it had 1 or 2 megabytes of RAM. The Mac had 128K. K.

No, my office isn't crowded, why?

This was quite a production. I had files that purportedly contained the Dali Clock executable, that had been floating around in my home directory for a decade, and I needed to find a way to get those files onto the Mac.

The problems standing in the way of this:

  • 128K Macs didn't have ethernet (ha!) or SCSI (are you joking?)
  • I think they might be able to run AppleTalk over the serial port, but I don't have the drivers for that -- so I'd have to find them, and install them, which is something of a chicken-and-egg problem.
  • 128K Macs can only read 400K single-sided floppies.
  • No floppy drive manufactured in the last 6+ years can read or write 400K disks. (Or the 800k double sided variant.) Apparently modern disks are made of different material and are written with a different magnetic field strength, so it's a hardware issue, not software.
  • No Mac that does have a disk drive that can write 400K disks also has ethernet.
  • For that matter, no Mac manufactured in the last 3 (?) years comes with a floppy drive at all!

So, here's how I did it. Barry loaned me a Mac Classic II that he had lying around (it's toaster shaped, but has a hard drive! Oh, BTW, you could get a hard drive for the original Macintosh: it plugged into the serial port.) I used the Classic II to format a modern floppy disk. I tracked down a USB floppy drive. I downloaded the files used an iMac, and wrote them to that floppy. (The iMac can read disks formatted on the Classic II but not vice versa.) I got the files onto the Classic II's hard disk that way.

Then I had to figure out how to unpack the files, because there were several layers of decade-obsolescent packager formats wrapped around them, the trickiest of which was PackIt (which apparently only Jurassic versions of Stuffit Expander can read: versions which only run on Jurassic Macs...)

Finally, I formatted a 400K disk on the 128K Mac (a disk that came with it, i.e., a disk manufactured in 1984) and copied the files from the Classic II's HD to that. And, success!

The original (Steve Capps) version of Dali Clock only works on the 128K Mac: it crashes the Classic after one second. However, in 1987, Ephraim Vishniac disassembled the original clock binary and hacked it to work on (then-) modern Macs. So (for the sake of completeness) I was able to get his version working on the Classic II (OS7.) Sadly, that version does not work on OS9 or OSX, though surprisingly, it doesn't crash OS9. It seems to be assuming a 1-bit display, so you just get some static at the top of the screen.

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4 Responses:

  1. ralesk says:

       Wow, nice desk :D  And left positioned mice :D

       As for xdaliclock... lessee what it does under my cygwin >:}

  2. cyantist says:

    That's sooo awesome. I can't wait to see it.

  3. jlindquist says:

    The 400/800K disk difference isn't a matter of materials, it's a matter of rotational speed. They're the same double-density floppies as used on PCs of the era, but the Mac drives ran at progressively lower speed on the outer tracks, to squeeze more data onto them. I am told by an ex-Navy (stationed in Japan) former co-worker that "odd" hardware like that is more common in Japan, used on the non-Wintel systems that are more common there. They're not custom Apple mechanisms, they're just not off-the-shelf parts here in the States.

    I recall software existing to read those disks on a PC, I assume they used Stupid Hardware Tricks to mess with the PC floppy's speed. I don't think the software was totally reliable, and I doubt you could write to them. There *are* ethernet-capable Macs that can write 400K floppies, you just have to run System 6 on them. (You can do it under System 7.0 or 7.1 too, but it's a pain in the ass according to an Apple Tech Note.)

    I know. More than anyone ever wanted to know about Mac floppies. Sorry. I've spent a piece of my weekend trying to resurrect data from 12-year old HyperCard stacks, so I've been neck-deep in ancient Mac lore.

    The better hard drives (indeed, Apple's own 20-meg drive) for the 128K used the floppy port. And AppleTalk indeed runs over the serial ports (I think the system software restricts you to the Printer port,) you just have to find the 9-pin version of the LocalTalk or Farallon PhoneNet dongle. (WeirdStuff always has a few whenever I'm there.)

    I have a 128K Mac I picked up at a ham auction a few years back ($5, nobody else wanted it.) I thought I'd do the fishtank thing, but I like the conversation-piece clock idea much better... :-)

    • jwz says:

      The rotational speed issue is why it's (generally) not possible to read Mac disks in a PC. Mac drives had variable-speed motors, and they would put a varying number of sectors per track (more sectors on the outer tracks.) I believe Amiga disks are the same way, which is why getting bits into a PC from an Amiga is also damned near impossible.

      But according to AppleCare 3427, you still can't use a modern ("high density") floppy in an old (400k or 800k) drive:

      High-density media should NOT be formatted in a 800K or 400K drive.

      High-density disks are physically different from double-density disks and are tested to a different specification. The coating on high-density disks is thinner and has finer particles. These disks require a less intense magnetic field from the read/write head to properly align the magnetic particles within the data cell during a write cycle.

      The magnetic field generated by Apple 800K and 400K drives is too strong and may cause data loss.

      In any event, it's empirically impossible to format a modern floppy in a 128k Mac. When I put the disk in, it didn't even recognise that there was a disk there. Then I tried taping over the extra hole, and that made it recognise it; but when trying to format it, it always said "formatting failed."

      Rumor has it that OfficeMax still sells DS/DD floppies, though, so that means that it's at least possible to obtain recently-manufactured blank media. That's a relief...