Apple ][ Disk Emulation

A while ago, [Steve] over at Big Mess ‘O Wires created a device that would emulate old Macintosh disk drives, storing all the data on an SD card. No, it’s not SCSI; the early Apples had a DB-19 connector for connecting 400 and 800kB disk drives. It’s a great piece of hardware for bootstrapping that old Mac you might have sitting around. Apple ][s, IIs, and //s use an extremely similar connector for their disk drives. A few rumors on some forums led [Steve] to experiment with some ancient bromide-stained boxes, and the results are interesting to say the least.

After pulling out an old //e and IIgs from storage, [Steve] found his Macintosh Floppy Emulator didn’t work with the Apples. This was due to the way Apples could daisy chain their disk drives. There’s an extra enable signal on the connector that either brings Drive 1 or Drive 2 into the circuit. Macs don’t care about this signal, but Apples do. Luckily the 800kB drives for the IIgs have an extra board that handles this daisy chain and drive eject circuitry.

After removing this extra board from a IIgs drive and connecting it to the Floppy Emu, everything worked beautifully. With schematics and a working circuit in hand, it’s now a piece of cake to build an adapter board for using the Macintosh Floppy Emu with Apples, or to build that circuit into a future revision of the Floppy Emulator.

Considering how much trouble [Steve] had bootstrapping these Apples without an SD card to Floppy drive emulator, we’re thinking this is great. The current way of making an Apple II useful is ADTPro, a program that uses audio to communicate with Apples over the cassette port. In case you haven’t noticed, microphone and headphone ports on laptops are inexplicably disappearing, making a hardware device like a SD card floppy emulator the best way to bring disk images to 30-year-old hardware.

Rewritable ROM for the Mac Plus

The Macintosh Classic – a small all-in-one computer with a 9″ monochrome screen –  was one of the more interesting machines ever released by Apple. It was the company’s first venture into a cost-reduced computer, and the first Macintosh to sell for less than $1000. Released in 1990, its list of features were nearly identical to the Macintosh Plus, released four years earlier. The Classic also had an interesting feature not found in any other Mac. It could boot a full OS, in this case System 6.0.3, by holding down a series of keys during boot. This made it an exceptional diskless workstation. It was cheap, and all you really needed was a word processor or spreadsheet program on a 1.44 MB floppy to do real work.

[Steve] over at Big Mess O’ Wires had the same idea as the Apple engineers back in the late 80s. Take a Macintosh Plus, give it a bit more ROM, and put an OS in there. [Steve] is going a bit farther than those Apple engineers could have dreamed. He’s built a rewritable ROM disk for the Mac Plus, turning this ancient computer into a completely configurable diskless workstation.

The build replaces the two stock ROM chips with an adapter board filled with 29F040B Flash chips. They’re exactly what you would expect – huge, old PDIPs loaded up with Flash instead of the slightly more difficult to reprogram EEPROM. Because of the additional space, two additional wires needed to connected to the CPU.  The result is a full Megabyte of Flash available to the Macintosh at boot, in a computer where the normal removable disk drive capacity was only 800kB.

The hardware adapter for stuffing these flash chips inside a Mac Plus was made by [Rob Braun], while the software part of this build came from [Rob] and [Doug Brown]. They studied how the Macintosh Classic’s ROM disk driver worked, and [Rob Braun] developed a stand-alone ROM disk driver with a new pirate-themed startup icon. [Steve] then dug in and created an old-school Mac app in Metrowerks Codewarrior to write new values to the ROM. Anything from Shufflepuck to Glider, to a copy of System 7.1  can be placed on this ROM disk.

This isn’t the first time we’ve seen ROM boot disks for old Macs. There was a lot of spare address space floating around in the old Mac II-series computers, and [Doug Brown] found a good use for it. Some of these old computers had optional ROM SIMM. You can put up to 8 Megabytes  in the address space reserved for the ROM, and using a similar ROM disk driver, [Doug] can put an entire system in ROM, or make the startup chime exceptionally long.

iPad Finds New Home in Mac Classic

Who of us out there don’t have a spare iPad and Mac Classic kicking around? If you are one of those lucky folks then this project is for you. [site hirac] has made a pretty neat stand for an iPad made out of a Mac Classic case (translated). It just happens that the screens of the Mac Classic and iPad are pretty darn close in size. Although the screen size is similar, the resolution is not. The original Macintosh Classic had a black and white screen with a resolution of 512 × 342 pixels. The iPad’s resolution of 1024 x 768 pixels has 450% more pixels than the original Mac.

To get the iPad to fit correctly, the case had to be significantly modified. First, all of the internals of the Mac were removed, leaving just an empty case. The front panel of the case was removed and a slot on the left side is made. This slot helps to allow the iPad to slide into the Mac. On the inside of the front panel quite a few of injection molded supports were trimmed away for clearance. A slot was also cut in the left side of the rear case half. When the case is re-assembled, the slots in the front and rear halves provide a large enough hole for the iPad to fit through. Oddly, there are some plastic features on the front panel that are at just the right height to hold the iPad in the ideal location to line up with the screen cutout in the case.

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Fail of the Week: CPLDs That Release Blue Smoke

fotw-floppy-emulator-burned-cpld

The card you see above is a floppy drive emulator for Macintosh. [Steve Chamberlain] has been hand assembling these and selling them in small runs, but is troubled by about a 4% burn-out rate for the CPLD which has the red ‘X’ on it. He settled into figure out what exactly is leading to this and it’s a real head-scratcher.

He does a very good job of trouble-shooting, starting with a list of all the possible things he thinks could be causing this: defective part, bad PCB, bad uC firmware, damage during assembly, solder short, tolerance issues, over-voltage on the DB connector, or bad VHDL design. He methodically eliminates these, first by swapping out the part and observing the exact same failure (pretty much eliminates assembly, solder short, etc.), then by measuring and scoping around the card.

The fascinating read doesn’t stop with the article. Make sure you work your way through the comments thread. [Steve] thinks he’s eliminated the idea of bad microcontroller code causing damage. He considers putting in-line resistors on the DB connector but we wonder if clamping diodes wouldn’t be a better choice (at least for testing purposes)? This begs the question, why is he observing a higher voltage on those I/O lines during power-up? As always, we want to hear your constructive comments below.


2013-09-05-Hackaday-Fail-tips-tileFail of the Week is a Hackaday column which runs every Wednesday. Help keep the fun rolling by writing about your past failures and sending us a link to the story — or sending in links to fail write ups you find in your Internet travels.

Putting A Mac Plus On The Internet

plus

[Jeff] has a Mac Plus, an 8 MHz computer with 4 MB of RAM and a 512×342 1-bit screen. It was his first ‘real’ computer, and like those guys that take Model A Fords out for a Sunday drive, [Jeff] decided to put this old box on the Internet.

A Plus has a few options to get on the Internet. The best, but most expensive, is a SCSI to Ethernet computer. For a somewhat slower connections, a PowerPC mac can be used as an Ethernet to Localtalk (the Macintosh serial port networking protocol) bridge. Lacking either of those pieces of hardware, [Jeff] decided to use a Raspberry Pi. The Pi does the heavy lifting, and a handful of serial adapters and voltage converters turns the Pi into something that can talk to the Plus’ serial port.

Even with the MacTCP stack and the MacWeb browser, there are still some things this ancient computer couldn’t do. HTTPS hadn’t been invented until 1994, cookies are just a pain, and CSS is right out. This means modern websites (except, of course, the Hackaday retro edition) simply won’t render properly. To fix this issue, [Jeff]’s friend [Tyler] came up with a Python script using Requests, Beautiful Soup, and Flask to strip out all the Web 2.0 cruft, handle the cookies, and to get rid of SSL.

The end result is a Mac Plus with 4 Megabytes of RAM on the Internet, able to pull up Wikipedia and Hacker News. It isn’t fast by any means – in the video below, it takes about five minutes to pull up the front page of Hacker News – but it is a 27-year-old computer on the Internet.

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A one third scale Macintosh

minimac

Released in 1984, the original Macintosh was a wonder – not only did it have a GUI and a mouse, it was actually one of the smaller computers of the day. Now that we’re nearly 30 years past the release of the OG Mac, it follows that a smaller version should be possible. [John] did just that by creating a 1:3 scale replica of the original 128k Mac.

As you would expect, this tiny Mac is powered by a Raspberry Pi running Mini vMac, an emulator for these olde tymie 68k Macs. The display is a 3.5″ LCD with a resolution of 300×200, not quite up to the standard classic mac resolution of 512×342. At least this version has color, though.

Also inside the carefully crafted PVC case are a WiFi and Bluetooth dongle, along with an off-the-shelf phone charger. It’s a remarkable piece of craftsmanship, and given the games and applications (i.e. Photoshop 1.0) available for these old Macs, its possibly more useful for general computing than a stock Raspberry Pi.

You can check out the video walkthrough of everything this tiny little Mac can do below.

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Debian Linux on a PowerMac 7200

debian-7200

Those of us that run Linux on a modern or nearly-modern PC know that it’s a capable operating system.  It’s also (at least in my case with Ubuntu) extremely easy to install on a semi-modern computer. On a mid-90s era PowerMac 7200, things aren’t quite so simple.

In a testament to both his technical ability, and possibly even more so his tenacity, [Chris] was able to get Debian 6.07 running on a PowerMac destined for destruction. He had slated a few hours to upgrade this 56 Megabyte monster, but it turned out to be a several-day event. Those that are well-schooled in Linux may find the hairy details useful, and some more background can be found in part one. This project was a stepping-stone to something else, so we’re anxious to see what the end result is.

If you find this interesting, feel free to check out the retro edition of our site. It’s not entirely about ancient computers, but it can hopefully be displayed on one.

via [twitter]