build the first MC6847 video display 'warmup' computer.
i have found three projects based on the 6502 which make use of the MC6847 and have published their schematics. so far so good. when the parts arrive i have to trust my breadboards and little wires are of a sufficient quality as not to bounce and ring, we're dealing with sub-1 MHz TTL-level digital signals so.... maybe my dodgy tools and components will be good enough.
build the first permacomputer prototype
the next step after i have honed my practicals skills on a simpler task is this: construct a custom video display for the permacomputer, based on the information contained in don lancaster's cheap video cookbook or here if you wanna support the internet archive?
the reason for using custom logic for the display is the limited number of columns the MC6847--it is my hope to have 40 columns, not a mere 32. i wish i could say more, but the short story is this: using EEPROMs in place of discrete logic is the ticket to having a simple design.
the CPU. the motorola MC6800. once quite popular, but somehow overlooked a little, imho, with the retro computing revivial of the 2010s. it runs lots of operating systems, like CP/M, FLEX, and more.
this is the original chip that the 6502 team decided to try and radically simplify with their design. they were right. the 6502 reigned supreme.
MC6875
this is the 6800's external clocking logic. if you csn get one, your life will be easy. it will do all the clocking really well. this is an exotic chip now, however. ngl, at the price i got this, i will be hoarding them.
this fits into the main cpu subcircuitry. we just need to get some passive components and then a 4 MHz crystal.
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DMA Video Logic
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these two lil buddies are the CD4014, and CD4040, respectively.
they do the main clocking and signalling for the composite out video.
the 4014 is a parallel in serial out shift register or buffer register. then the 4040 is a binary counter. you get the idea.
please refer to the DREAM6800 schematics.
these chips allow us to do DMA graphics @ 64 columns by 32 rows as a dot matrix.
256 bytes of RAM in the DREAM's memory map are simply pixels in RAM
Miscellaneous
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1. a now very exotic LM566. not a 555 it's a really interesting VCO. voltage controlled oscillator. not surprising, it's from the digital audio in ciruitry. HAM lovers watch this space.
A permacomputer is a computer which attempts to embody the virtues of
permacomputing.
Foundationally, permacomputing itself is set of community practices
and traditions which shares a set of social and ecological values
inspired by the 70s land management and settlement design of
permaculture.
What is the point of this project?
The people's permacomputer project is an attempt to physically
realise a permacomputer.
This will involve not just the production of an actual model
permacomputer, but also the development of a list of suggested social
and cultural practices around computing that will, it is hoped, assist
in the continued human practice of electronic computing.
There are many different dialectical approaches to making an
introduction to the people's permacomputer. One thought experiment
that has proved especially popular and easy to grasp sums up the
mindset behind which we are functioning:
Industrial society has collapsed. All semiconductor fabrication has
ceased, society-wide electrification is no longer guaranteed. There
is no longer any internet. Computing as it was once known in the early
21st century is impossible. You need a computer for a task. What do
you do?
This project is a humble response to the challenge posed by the above
problem.
Adventures in the traditions of computation
We seem to take it for granted that a computer in everyone's hand just
is democratic computing. Indeed, the ubiquity of contemporary
computation has been confused for 'democracy'.
As quickly as we marched towards computing for the masses, we marched
just as swiftly away.
GNU
There do today however still exist flourishing movements which are
worthy of mention--although not exclusive in this honour, much of the
GNU movement is to be credited with any sanity being preserved in
present-day mass computation.
Hobbyist computing
The hobbyist computer movement of the 1970s was rich in ideas, and
courageous--sometimes breathtaking--in its efforts to allow the lay
person to realise their access to an electronic computer.
Need we speak of the heterogeneous array of kit computers and their
attendant clubs and magazines? Some of mention are entire influential
computing platforms in their own right:
Altair 8800.
Apple I and II.
Commodore 64 and the VIC-20.
From minicomputers to microcomputers
One may even be able to recount the history of computing before its
entry into the mass consciousness. Computer architectures from (now
defunct) firms like DEC (Digital Equipment Corporation) still carry
enormous significance today.
Much of DEC's fascinating and progressive work culture is imprinted on
the fruits of their labour. Two models of computer from DEC in
particular, the PDP-8 and the PDP-11, are steeped in the corporation's
ethos: "do the right thing".
Neither of these machines were of much relevance outside the academy
and industry, but they represent huge strides forward in human history
for the virtues that the people's computer committee see as necessary
for permacomputing.
In particular, the full plans and maintenance manuals for each token
computer were accessible alongside each physical device:
When was the last time the entire structure of a modern smartphone was
exposed and made accessible to the user? Indeed, the devices we take
for granted today are deliberately obfuscated for the purpose of
unchecked economic profit.
Mutual exclusion
There are many influential projects which attempt to address the same
set of values driving the people's permacomputer project. Some worthy
of note can be listed in no particular order:
All of these projects are concerned with some subset of the principles
the permacomputer project holds dear. Collapse OS is software that
aims to be system agnostic, and assumes the previous acquisition of
some supported hardware.
The uxn ecosystem is rich and continues to flourish. However,
while this project shares much with our own concerns for
sustainability and the long-term persistence of electronic computing,
we diverge from uxn on one fundamental point: we aim to
physically provide the community with complete systems that are
easily turned on and interrogated by the lay computer user.
That is not to say uxn does not also shine in such areas, but
uxn is (very consciously) an emulator. The people's computer
project aims to quite literally place completed general purpose
computers into people's possession.
While one horn of the dilemma may be expressed as "software without
dedicated hardware", the reverse can be said to be true of the plethora of projects similar to the RC2014, and Ben Eater's breadboard
6502 project. In this case, it is "hardware without dedicated
software".
These two aspects of a general purpose computer--its own unique
physical construction, and its capacity to perform abstraction through
judicious programming--are usually siloed off from one-another
intellectually.
In this way, the people's permacomputer is an attempt to blend, and
thoroughly combine two previously mutually exclusive set of practices
which, even if they were only able to survive the collapse in part,
are invaluable when applied correctly.
Permacomputing and heterogeneity
Our research was long and laborious. When the results of our
information gathering started to become clearer, we discovered that it
was not appropriate to offer up one model of permacomputer, but
several.
The DREAM's 'older brother': a more powerful permacomputer able to
deal with more complex human demands.
Permacomputers constructed from salvage, such as e-waste. One such
proof of concept we imagine demonstrating is the collection and
repurposing of ESP32C3 microcontrollers from inside 'smart
lighting'.
Permacomputers derived from popular off-the-shelf contemporary
microcontroller kits, like the Arduino Uno or Mega.
Each of these four approaches manages to present a view of the
fundamentals of computing from a different perspective. It seems to
us, at least, that there are various competing demands that must be
balanced delicately in order to run a community organisation. There is
no 'one size fits all'.
A mnemonic can be derived from the four computer models we humbly
offer up to solve your computing woes:
I am having difficulty sourcing parts. I laboriously inputted and was able to locate every part on aliexpress, but multiple items from the same vendor would not cause a saving in the postage.
Does anyone know a more equitable method of sourcing the parts listed in this PDF?
Much appreciated.
Blair Vidak.
Please find reproduced below the schematics for the DREAM6800 computer.
Power:
-** Cassette circuitry. Kansas PSK encoding.- *** CPU and Clock generation via the Motorola 6875:** Video Display Generator (composite video):
The keyboard circuitry, implemented by the Motorola PIA:
Current smoothing capacitors and auxiliary circuit definitions: Memory:
The full listing for the CHIPOS interpreter / monitor program resident in 1K ROM:
The People's Permacomputer Project (acronym: P3) is designed to meet a special design case. That is: modern digital civilisation has collapsed. Complex computer hardware is hard to come by, and will not be easy to repair. This hardware project will also attempt to meet a use case scenario: storage upwards of 200 years, and be durable enough to still operate.
It is my hope this permacomputer will truly be able to last around 500 years with minimal need for maintenance or repair.
~The Nipkow Disk Video Teleprinter~
Please refer here. the hellschreiber is a shortwave radio compatible facsimile device. In other words, the hellschreiber is a type of radio fax machine.
The principle behind the radio fax is similar to a mechanical televison. Instead of using ink to print onto paper, the television uses a nipkow disk to scan across a flashing light source, such as an LED or fluorescent tube. The flashing light is timed to the position of each of the holes in the nipkow disk, allowing luma pulses to be created, mimicking pixels on an electron-beam CRT.
~Construction of the Mechanical Video Teleprinter~
The first movement of this project is to design a mechanical television. This stage of research and development will be considered a success if an operating 30-scanline nipkow disk television can be built.
Why? Because video is important for the human-computer interface, and resources will be severely limited in terms of what will be able to provide a standard, as well as modular interface into the digital logic of the P3.
The mechanical television is a good choice for demonstrating the possibility of video output from a digital computer after the collapse of modern society.
Please find attached the research material from the Ben Heck show.
Episode #1
Episode #2
Suffice it to say: you construct a 30 line televisor @ 15 FPS with the following materials:
- a cheap electric drill - some vinyl LP records - a cheap LED or fast fluorescent light
This construction is a happy congruence with the processing limitations of the digital computer to which the mechanical TV will be attached. It will only be capable of 30 scan-lines of resolution.
Please refer to the reference images of what i imagine this mechanical TV will be able to render.
Blair Vidakovich
