What is it?
The SC-1 as its being tentatively named, is an
attempt at a modular S-100 style minicomputer.
Yes, I said that correctly,
minicomputer, not
microcomputer. A simple way to think of this project is, a big
RC2014 kit.
Minicomputer is a term for machines that fit
somewhere between the old full-room mainframes
of the 1950's and 60's and more into the server-rack
sized devices of the 70's. The PDP series
of machines starting with the PDP-8 are a great
example something often considered a "minicomputer",
as opposed to the "microcomputers" able to fit on a
single desk like the commodore 64, or TRS-80.
Why?
Bigger = cooler
What does that mean for me?
The point of creating this is to have an easy to
assemble, fun to build, hobbyist computer that
can hopefully help teach the function of computers
better than many of the "plug stuff in and solder it"
type kits already avalible to be put together. But
with the added bonus of having a cool full sized
machine unlike the FPGA, Raspberry Pi, or other
system-on-a-chip type reproductions out there.
You can slap this inside a woodgrain box covered in
dymo labels like its 1975, or you can fill a
whole server rack to feel like you've snuck a Data
General machine out of a museum when no one
was looking, or perhaps somewhere inbetween.
What are its Specs?
I'm aiming for a 4U rackable design using
pre-existing rackmount solutions for the main case.
Being that the machine is intended to be modular,
the exact specs will vary from one system to
another. The system will use an S-100 like backplane
allowing users to add additional memory,
peripherals, and even swap out CPU's if so desired.
What kind of Logic?
Chips get old just like we do, so first and foremost
the goal is to require as few "vintage" chips as
possible. Partially to keep the cost down but mainly
you dont have to hunt for that $700 first run
Intel 8080. Whenever avalible, modern reproductions
or equivalences will be chosen as default.
With that being said the current plan is to have three options:
SC-1A
Standard integrated circuts where applicable and
sensible. this is basically just a Digital Group
machine clone at this point but without all the fiddly wirewrap.
SC-1T
Resister-Transistor Logic! Technically closer to
Diode-Reistor-Transistor logic, but regardless,
this is close to the intended use case to assemble
the machine. It'll be slow, it'll be big, and it
probably wont be the cheapest option, but it'll be
cool, and thats what counts. Some things are
just not practical as a purely transistorized
package, like memory for instance. There will absolutely
be "transistor memory cards" avalible if you like
that kind of torture, but there will also be more
modern integrated circut options to make use of as
well. It will take awhile to figure out the 8080
Z80 CPU's but a transistorized 6502 has already been
worked out and will be avalible in "card"
form for those who want to go
all in.SC-1R
Relay logic. For when you really want to run up your
electric bill and go deaf at the same time.
This is really going to have to be a separate
machine altogether and may get branched off as its
own project as a result, but its definately in the
plans. Again, like with transistors, some things just
aren't practical for a diy project, and so it'll be
a mixture of relay "cards" and transistor or integrated
circutry for the stuff that would otherwise fill up
your whole house let alone a single server rack. But,
just as with the transistors, the option will be there to go 100%
What will it look like?
It will have a very expansive front panel for
complete programming and manipulation without
the need of a terminal,a cassette interface for
saving and loading programs, an rs232 port for
when you get tired of flipping switches to load in
your programs, fans to keep you and your machine
cool (or warm, depending), and quite a few
expandable peripherals and features (like probably
an SD or CF interface for convenience).
Planned Options:
- CPU - Z80, 8080, 6502, custom non-integrated design
- Memory - 1, 4, 8, and 32k boards, probably more.
- Front Panel - less altair, more IBM 360 :)
- Data Input - Cassette interface, rs232, front panel, paper tape/punch card
- Video - RS232 terminal, VGA, possible RF or composite video out
Peripheral "card" modules:
- RS232 serial, a very simplistic serial card to use with your own supplied terminal.
- ESP32 (or simmilar) Wifi + Modem, to connect to your favorite BBS or home file server
- Magnetic Tape interface, for loading and saving programs via cassette or reel to reel (or mp3)
- Integrated Terminal, with more modern video out options and a keyboard interface.
- Floppy/HDD controller, for use with real drives, or with gotek solutions.
- SID sound chip, using FPGASID
- Custom sound chip.
- various other peripherals as ideas come to mind and iron goes to pcb.
Accessories:
- Paper Tape/Punch reader
- Punch card memory, ala FACOM 128
- DIY keyboard, to also be used with other kit computers or terminals as well.
A "bog standard" machine will be a z80 cpu, 8kb of ROM, 32kb of RAM, and a serial card or
front panel interface (It will be possible to use the machine with only one or with both).
The front panel, although *strongly advised*, wont
be required. There will also be plans to build
a case for the machine from easy to aquire standard
sized lumber if you dont want a rack at home.
What does it do?
The current plan is to have the machine be capable
of running CP/M and Basic, with the potential
of additional options as time and development
provides. The purpose of this is to allow the
extensive amount of software and documentation
already in existance for those (and others) to be
run on the machine. Programming may be fun, but its
a lot more fun when you can have a backlog
of existing code to run on your cool new toy. I also
like the idea of being able to make a "big Sinclair",
or a "big Commodore" which should be totally
possible with reproduction and compatable parts.
So is this an S-100 machine?
No. It will use "cards" and a backplane like one,
but it wont be compatable. I dont know yet how
many pins it will use as of yet, that will be determined as the design progresses.
Can I build one?
Of course! much of the project will be "open source"
and I'll make sure to sell runs of boards for
others to build themselves. I may even consider
offering files to let you etch your own PCB's from
copper plates.