News Passionate enthusiast builds a fully functional processor out of old memory chips — hand-solders every wire, writes 1800 lines of assembler code, a...

[Admin]

Someone just built a fully functional CPU from scratch using old memory chips and logic parts from the 8-bit era. Spanning four perfboards and over a kilometer of wire, it runs real code, handles interrupts, and even plays The Matrix—all using logic simulated entirely through EPROMs.

Passionate enthusiast builds a fully functional processor out of old memory chips — hand-solders every wire, writes 1800 lines of assembler code, a... : Read more

 

[bit_user]

When I started dabbling with digital circuits, I very quickly moved from breadboards to schematic simulation programs. Way faster and easier, more scalable, and not limited by bench space or what components you had on hand. And that was like 30 years ago.

This is a cool hack, though. Impressive commitment to see it through to a fully-working system. The lookup-table approach obviously doesn't get you very far, but it's okay for 8-bit. One interesting consequence is that expensive operations, like integer division, take just as long as cheap ones, like addition or bit-wise ops. As for things like trig functions, are these just 8-bit approximations? Seems hard to believe it actually implements IEEE754 floating point.

I'm guessing that playback of the Matrix was just blitting some frames that were either uncompressed or cheaply-compressed, because there's no way this thing has the horsepower to decompress any sort of modern video codec.

 

[MisterZ]

Why was the title of this article changed? Originally it read: "Madman builds a fully functional CPU from old memory chips"

 

[bit_user]

Why was the title of this article changed? Originally it read: "Madman builds a fully functional CPU from old memory chips"

I'd guess that it's because calling someone a "madman" could be offensive. It's a little eccentric to do something like this, but really shouldn't be associated with mental illness.

 

[JRStern]

I don't understand what he did.
Somewhere you need to add some logic, which may be extremely limited but it still has to be there.
The rest is just building a minimal Turing Machine, which can indeed be very simple.
But he didn't stop at simple if he built in trig functions ...
... but I still don't get what was done, or why.

 

[King Anfalas]

Just take the blue pill and be happy.

 

[bit_user]

I don't understand what he did.
Somewhere you need to add some logic, which may be extremely limited but it still has to be there.

Yeah, it does. However, most of the ALU is implemented using lookup tables in the memories. As far as I understand it, his idea is basically to use lookup tables wherever possible and minimize the amount of actual logic.

... but I still don't get what was done, or why.

Sometimes, you get an idea for how to do something and want to try and see if it actually works. Then, maybe you want to see how far you can push it (i.e. how well it scales). Even if it doesn't pan out, you can usually learn something in the process. Simply asking "what if?" can lead a lot of interesting places.

While this architecture makes zero sense for classical digital computers, perhaps it would make a lot more sense in a domain like biological computation or optical computing?

 

[davet542]

Someone just built a fully functional CPU from scratch using old memory chips and logic parts from the 8-bit era. Spanning four perfboards and over a kilometer of wire, it runs real code, handles interrupts, and even plays The Matrix—all using logic simulated entirely through EPROMs.

Passionate enthusiast builds a fully functional processor out of old memory chips — hand-solders every wire, writes 1800 lines of assembler code, a... : Read more

Ben Eater (eater.net) and James Bates (https://www.youtube.com/@jimmyb998) did this 7 years ago using breadboards, logic chips and eproms. They did an excellent job of documenting their designs. Although this computer sounds to be more elaborate, Ben Eater's and James Bates' work should have been acknowledged. The article implies that this builder had done something new. Others have even made circuit boards of the Ben Eater/James Bates design.

 

[bit_user]

Ben Eater's and James Bates' work should have been acknowledged. The article implies that this builder had done something new. Others have even made circuit boards of the Ben Eater/James Bates design.

Fair, but there are few truly novel ideas in tech. All of these underlying ideas go way back, many decades, even if (and I wouldn't bet on this) nobody took it to the logical extreme that we see in these examples.