This homebrew 4-bits computer is made of nands, diodes, transistors and passive components. Its program is encoded by LEDs.
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It is usual to make a ROM using a diode matrix. If the classical switching diodes are replaced by LEDs, the bits of the addressed word that have the value 1 illuminate. This allows you to view the execution of the Nand 565 program.
A new version with giant LED displays, running an intriguing algorithm :-).
Can you guess the last number before 0000 ?
nand-565.pdfDescription and schematicsAdobe Portable Document Format - 3.59 MB - 12/17/2017 at 17:47 |
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Yes, the TD4 is more integrated, but in the same spirit :-).
Agreed, nothing like NAND gate decomposition. Its just one step above transistors or even relays.
Hey! Cool project - Too simple and clear architecture! But think I spent a lot of time to design it.
My respect!
I's your instruction set is Turing-full or not? I understand that the whole computer is not - you just have not enough instructions to program.
Yes, this instruction set IS Turing complete under the assumption that the size of the registers (currently 4 bits) can be arbitrarily extended. With n-bits wide registers, a Turing machine with a tape of length n can be simulated.
My version of the Turing Test is whether I can emulate another (simple) CPU (such as TTA (Transport Trigger Architecture) or SubLEq. The TD4 which has only 16 instructions but can emulate a TTA CPU (at least my slightly modified version does as it has an extra output port). Generally to be Turing Complete all you need is a NAND or a NOR gate and enough memory (refer to the NOR Machine). SubLEq has only minus but like sofware division you can implement boolean functions in software as well.
So it is rather amazing how little can be Turing Complete.
Olivier Bailleux
AndyMac
Wim Van Gool
jay-t
Pavel
Discrete finite state machine with NAND gate level logic, nice. Well done. You may be interested in the TD4 a Japanese 4 bit that is not that different to yours (https://www.youtube.com/watch?v=_Ztb2PwnVPc). The TD4 is a bit more "show" than "computational" compared to yours.