i am most likely going to begin casually constructing a discrete transistor computer of some form this week. i have been planning this since 2013.
i
first started getting interested in computers again, at that time,
after i got i got very sick in 2013. it seemed like a pretty cool
interest area to re-explore while i was having a convalescence.
i originally designed this computer, the RAVEN, following the MENTAL- series of computers, which i thought would be simple in execution. i think it still would be, but,
after studying hardware LISP machines, i am going to abandon the
original plan i had for the RAVEN, and instead build the MT15 computer
that is outlined by 'Deiter' here: http://www.6502.org/users/dieter/mt15a/mt15a_1.htm, because it effectively /IS/ the
architecture of a LISP machine.
for instance, look at the data path of the mid-to-late 1970s CADR from MIT:
...and compare it to Detier's MT15:
i am planning to take lots of
photos and make lots of videos documenting, all of which will go on the
fediverse, my blog, and onto my new peertube.
I have switched to literal old school breadboard construction because it is very cheap.
The nails and wood are all reused.
I have also ditched SMD transistors and resistors because dead bug construction with them is too difficult.
I attempted using screws, but they were too big.
Almost all the components have been added, except for the 1N4004 power diodes.
This construction took an afternoon with a hammer and punch. First you tap the nails with a punch, and then hammer the nails.
I estimate this project could be assembled by children, with supervision. The children could used pre drilled wood, and be given small screws with washers.
I will solder the components to the nails once they have all been added.
I will post videos of the operation of the flip flop once I have completed the power supply.
I wonder if it's possible to find second hand 1N4148s in large quantities in Australia...
Loads of this project has used waste materials. Also it encourages technological independence. I will potentially rename this computer the 'Walden', after Henry Thoreau, whose philosophy this computer embodies.
The image below are three input triggers for a flip flop.
The following are my first efforts at making the direct set and clear circuit for the flip flop:
This is a plane-level view of the triggering sub-circuits:
I can prepare a how to guide about how to solder these circuits. It is a little fiddly but not difficult without a magnifying glass, although I would recommend one.
Just purchased the right exotic transformer (not really), some solder, and a small voltage regulator!
When we come to the core memory there will be some real power needed, but I think this 100VA dual, tapped secondary transformer will be enough for the whole CPU, excluding the core memory.
Blair Vidakovich
