Cat whisker (solid state) diodes have been around forver.
The Amateur Scientist from Scientific American may be usefull
for ideas. Organic (plastic) transistors may be another option.
Negitive resistance devices like NE2 tubes and Zinc/Oxide devices
also would make a intersting computer.
Mass storeage is easy, just have a good set of machine tools.
Mother earth news is a good read on other topics.
To my knowledge, operable diodes were among the first vacuum tubes and crystal diodes were first developed for RADAR applications in 1945. Am I missing something?
(The semiconductor diodes used in detector radios were of very varying quality, which is why there was this pin to find a suitable spot on the material that would do the job. I wouldnāt consider this in the margins required for automatic operations.)
Computer Engineering (a DEC view of hardware design) by Gordon Bell
pdf a good reading. The PDP 8 is a modern of the PDP 5, a machine designed to be 12 bits wide.
From the same book, the price of (semiconductor) memory per bit in cents per bit is: p = .3 * .72^(year-1974). Core memory ~ 1 cent a bit
at the same time. PDP8/E PDP11 PDP15 all came out in 1970 with the PDP 15 having the fastest memory and the biggest price. The PDP 11 with lower cost memory and the PDP 8/E the lowest speed and slowest cost. 1.2 us cycle time vs .8us cycle time for the PDP 15.
The current cpu I am building has 1.5 us core memory in a DE1 FPGA development kit, and 18 or 20 bitās wide. The Design is from
late 1974, permiting use of MSI TTL for the the data path, and
256x4 PROMS for microcode decoding. The current version is 18 bits
but design ideaās change often, thus FPGA development, rather than
cards of 74LSxx chips. Byte addresing and other factors led a 9 bit byte, so that a more complete instruction set be implimented,
including load constant on condition and branch on condition.
Push/pop are NOT implimented, but indexing off the SP
is permited.Indexing and Immediate are the only two addressing modes. The design is my version of a computer to compete with the PDP 11 and the other Small PDPās as well as the IBM 1130 and S100 systems.
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Now compare the 1.5Āµs (1964) of the original PDP-8 (1.2Āµs by the 1970s) to the 5Āµs of the PDP-1 (1959/60). ā The developments in the production of cores (they shrunk considerably) and in interfacing core memory (not that trivial) were enormous and exceeded in terms of gains in speed any of Mooreās Law, at least in the early years.
Speaking of bootstrapping technology after a hypothetical collapse, Iām not that sure, if this could be accomplished easily and at a reasonably price. There are stories of early European machines, when cores where still āhugeā, of core memory actually having been knitted by some elderly lady. Still, you had to come up with the cores in the first place and manage the engineering of the interfacing circuitry. (However, as indicated before, this is probably not the problem in this scenario, since, if there are plenty of salvageable Z80s left, there are probably also some of the interfacing RAM packages left, probably on the very same board.)
Otherwise: Core memory on an FPGA? Is this emulated core memory or are there FPGAs with real core memory? The project is interesting, let us know about the progress. (Personally, I always liked the idea of coming up with a slightly updated PDP-1.)
Well the core memory gives just the archecture model, for the read and write back cycle of main memory. The static memory on the FPGA development kit is hacked together with the cpu logic so it all fits timing wise and has speed that is normal for core memory at that time.
A early version was [B] [OP][ACC][INDEX][OFFSET]
with B=Byte/Word OP=opcodes AC=JCC/A/X/S INDEX=pc/zero/X/S
and SHIFT ac packed in there as well as the Classic FrontPanel.
I hope, we will never have to use a post-apocalyptic OS.
I wonder, if all computers are destroyed and someone has to use a Z80 from a toy.
How or where should he find or make this OS?
And what about a monitor, power supply etc?
You would need other things like food and water.
Another old thread surfacing - but this one is easy - How much computing could be done with a 4Mhz Z80 and serial terminal? Well - quite a bit WAS done on such systems running the CP/M operating system - many options for āself hostingā too - assemblers, BASIC, C, FORTRAN and COBOL compilers (they may not have been as full featured as on more capable systems, but they were there). Not to mention databases, editors (Wordstar!) and so on.
Networking didnāt quite make it before they faded from common use - but various file transfer systems using modems, null-modems and so on.
Mass storage - I had a Northstar Horizon with a 10MB fixed drive, as well as floppys in the university I worked in - we used it for industrial control applications. (But I have to say, BBC Micros were easier to use, program and interface as soon as we got them!)
However, In the āpost collapseā scenario then who knows, maybe my small collection of mechanical calculators would be valuable thenā¦ (Shades of āLogopolisā from Dr. Who with people working as āregistersā and computational nodes overseen by a āmonitorā. Actually, didnāt Feynman do that with people and mechanical calculators in parallel as part of the Manhattan Project?)
-Gordon
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Is it just me or did some discussion of the Z-80 underlie the technical aspects of that script? I remember some sort of breakthrough moment where the Doctor (or somebody) realizes that they can use āblock movesā to get past a problem. To me that is straight out of a list of potential advantages of the Z-80 ā the āblock moveā instructions like LDIR.
BTW, while Iām a big fan of the Z-80, I think the block moves provide some code compactness advantages but arenāt so much a big win when it comes to speed. I guess unrolled LDI instructions will beat out an 8080 but POP/PUSH are the ones that go the fastest and even then it isnāt clear youāre beating 6800/6502/6809 in terms of moving memory.
This thread makes me think of The Three Body Problem, which is sort of āpre-apocalyptic.ā They donāt have time or the natural resources to actually design and build computers, so the āemperorā simply emulates one, using his army. Every guy has a couple of flags and a set of rules for what to do with them. Computing is just a big logistics problem. 
Obviously, old computers could (and did) do very many useful things. But āusefulā is context dependent. What kind of apocalypse would leave the world in a state where computing was still useful but deny the use of the last 30 years of technology? I mean, my MacBook Pro that Iām writing this post with is 10 years old; I have 20 year old ThinkPads with WinXP and Ubuntu that I still actually use (running old software, hobby development), and 30 year old desktops that are kind of crusty, but still work. In what sort of apocalypse would I use my RC6502 to save the world and not my ThinkPad x23?
The only one I can think of is some kind of AI uprising (see Battlestar Galactica!) where modern tech is vulnerable, then strictly controlled, so that the underground resistance must reinvent in secret using sort of āmedieval computingā - blown glass vacuum tubes, forged wires, etc.
Workers calculate rows of pixels, return their sheets to the front for pixel rendering, and hang their completed worksheets on the wall
Human computing was a human-powered computer.
Collapse Computing
| Frugal Computing | Salvage Computing | Collapse Computing |
|---|---|---|
| Utilizing computational resources as finite and precious, to be utilised only when necessary, and as effectively as possible. | Utilizing only already available computational resources, to be limited by that which is already produced. | Utilizing what has survived the collapse of industrial production or network infrastructure. |
Collapse computing is on the tail end of not-being-able-to-make new hardware. A post-collapse society that has eventually lost all of its artificial computing capacity may still want to continue the practice of computer science in a purely theoretical level, as a form of mathematics.
Eventually you canāt assemble a thinkpad battery, fix the Macbookās USB ports, or make a new power supply from ductapped salvaged parts.
Collapse informatics is software engineering taking advantage of todayās abundance in computing power to prepare for a future in which current infrastructures have collapsed.
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Global Thermonuclear Warā¦ ie. the M.A.D. scenario where itās not just radioactive fall-out but the EMPs generated which will render a lot of electronic devices uselessā¦
However the knowledge will still live on in books (oops, lets keep paper copies and not store them in the cloud!) and living memoriesā¦
Shall we play a game?
(excuse me while I shield my 6502ās with tinfoil hatsā¦)
-Gordon
The paper copy for a retro-transistor
Scientific Americanās
THE AMATEUR SCIENTIST
Transistors. how to make thin film,
1970 Jun, pg 141