RETROCOMPUTING Antique Computers Run the World By Tom Owad
I was standing in the control room
of a power station, staring at the frozen screen of
the computer that controls the turbine system.
Reset it, and I risked corrupting a hard drive containing the only working copy of the long-obsolete
turbine control software. We had called the manufacturer for support and received the simple reply,
“We no longer support that model.” No software,
no parts, not even any advice was available for a
15-year-old computer responsible for keeping a 500-
megawatt power station operational. I hit reset and
held my breath, as I watched the system reboot.
With the system back online, I made an image of
the hard drive and tried to work out the system’s
idiosyncrasies so we could build a replacement for it.
The situation is not uncommon. I have another
customer that’s currently stockpiling old Macs so
they can continue to run a sophisticated custom
application they began developing in 1984.
Hobbyists and historians face similar difficulties.
Whereas the technology in an antique piece of
machinery is visibly apparent, a dead computer
tells one very little. The contents of the firmware
and the logic of the custom ICs slip away, leaving
a dead black box.
I had these problems in mind recently, while
devising a system to automate some 1960s manufacturing equipment for a customer. We’ve gone to
great lengths to use open source hardware and to
ensure that we have all the schematics we’ll need
to reproduce the circuit boards if they’re discontinued. One board uses a PIC microcontroller, of which
we’re about to order a lifetime supply.
Photograph by Dennis van Weeren
Open source hardware designs are becoming
common. Open Circuits ( opencircuits.com)
provides downloads and links to schematics and
printed circuit board layouts, and program files
for numerous open source hardware projects.
Opencores.org has a large repository of Verilog
and VHDL chip logic designs (known as “cores”).
These cores can be loaded onto FPGAs (
field-programmable gate arrays) as they stand, or
can be integrated into one’s own design.
Some of these projects are a boon to classic
computer enthusiasts who dread the day when
their machine boots its last. Syntiac’s FPGA 64 is
an entire Commodore 64, written in VHDL (a design
language for FPGAs), that can be loaded onto an
FPGA or the C-One microcomputer. For Apple
Dennis van Weeren’s tiny Minimig emulates the
venerable Amiga 500 personal computer.
users, Alex Freed took the 6502 in Syntiac’s design
and combined it with work of his own to create the
FPGApple, a single-chip clone of the Apple II.
Dennis van Weeren is nearing completion of his
Amiga 500 re-implementation, the Minimig. It
boasts an exact re-creation of the Amiga’s custom
chipset, and it currently runs on the Xilinx Spartan-
3 starter kit, along with two printed circuit boards
containing the M68000 processor and an MMC
memory card slot that supports the FAT16 file system
and can decode ADF disk images on the fly.
Code is also available for the Z80, 8088, and many
other processors and components. The FPGA in
the C-One can be reprogrammed to change the
system from a Commodore 64 to an Amstrad CPC.
A similar FPGA-based computer, the 1chipMSX, is
also under development, with plans to support the
Amiga, Amstrad CPC, Apple II, Atari ST, and Commodore 64 and VIC- 20 computers.
With the logic of these systems being preserved
in open-source VHDL and Verilog files, it may be
that if you want a program that will still function
50 years from now, your best bet is to write it on a
classic 8-bit microcomputer.
Tom Owad is the owner of Schnitz Technology, a Macintosh
consultancy in York, Pa. He spends his days tinkering and
learning, and is the owner and webmaster of applefritter.com.
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