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Show HN: I made a programmable computer from NAND gates

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Re: Show HN: I made a programmable computer from NAND gates

#41
Ground up projects like this are fascinating!

It’s also neat how “ground” has been deepening. It used to mean building mainframe from source. Then building a compiler. Now building from logic gates.

How much deeper can you get? Building a mainframe out of Gödel numbers?

Re: Show HN: I made a programmable computer from NAND gates

#42

Ground up projects like this are fascinating! It’s also neat how “ground” has been deepening. It used to mean building mainframe from source. Then building a compiler. Now building from logic gates. How much deeper can you get? Building a mainframe out of Gödel numbers?

One curious idea my friends have entertained is to go one level even deeper and emulate the very transistors that make up the NAND gates on the web, too. It would certainly spell disaster for performance, but it's without-a-doubt interesting.

Re: Show HN: I made a programmable computer from NAND gates

#43

NAND is popular probably because of nand2tetris, but it's worth mentioning that NOR is also a universal gate; and many early computers like the https://en.wikipedia.org/wiki/Apollo_Guidance_Computer#Logic... were entirely made of NOR gates.

I thought it's the other way around, nand2tetris used NAND because it was already popular? At least I remember hearing in university that NANDs are used for everything? Can't remember why they're used for everything though (and why not NOR, for example).

Re: Show HN: I made a programmable computer from NAND gates

#44

NAND is popular probably because of nand2tetris, but it's worth mentioning that NOR is also a universal gate; and many early computers like the https://en.wikipedia.org/wiki/Apollo_Guidance_Computer#Logic... were entirely made of NOR gates.

That's because in NMOS logic (maybe there's a symmetric reason in TTL, but I don't know for sure) you can implement a NOR with two parallel transistors between a pullup and ground, producing a zero output if either input is high. The symmetric NAND circuit requires two transistors in series, and therefore switches more slowly.

Re: Show HN: I made a programmable computer from NAND gates

#45

Ground up projects like this are fascinating! It’s also neat how “ground” has been deepening. It used to mean building mainframe from source. Then building a compiler. Now building from logic gates. How much deeper can you get? Building a mainframe out of Gödel numbers?

One curious idea my friends have entertained is to go one level even deeper and emulate the very transistors that make up the NAND gates on the web, too. It would certainly spell disaster for performance, but it's without-a-doubt interesting.

That would be fascinating!

Do you know any resources that document the transistor to logic gate translation?

Re: Show HN: I made a programmable computer from NAND gates

#47

Ground up projects like this are fascinating! It’s also neat how “ground” has been deepening. It used to mean building mainframe from source. Then building a compiler. Now building from logic gates. How much deeper can you get? Building a mainframe out of Gödel numbers?

One curious idea my friends have entertained is to go one level even deeper and emulate the very transistors that make up the NAND gates on the web, too. It would certainly spell disaster for performance, but it's without-a-doubt interesting.

Like... the physics?

If not, I think a NAND gate is made of just two transistors, so if you mean emulating how transistors should behave then I don't think it will affect performance more than ~50%

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