3 ms·

For an 8-bit CPU you could maybe do it. For a 64 bit cpu, the lookup table for addition alone would be massive. (You can of course do addition in smaller increm

For an 8-bit CPU you could maybe do it. For a 64 bit cpu, the lookup table for addition alone would be massive. (You can of course do addition in smaller increments, like adding one digit at a time and keeping track of the carry, but then you just have a normal full adder). The biggest issue is that this CPU would be conceptually simple, but very difficult to make fast. Memory is slow, and accessing a 64k lookup table uses more transistors than just doing the addition

_yb2s 2y ago
Again, I'm no expert here but find this stuff fascinating. Could the simplicity possibly allow some radically different CPU design that makes the lookups alone nearly instantaneous? I could imagine some types of optical/photonic physical 3D hash table structures - even ones where the same physical structure could support a large number of read operations in parallel if pre-arranged by a compiler to not physically interfere. I imagine a cpu with only one instruction could be physically miniscule, and therefore pack a lot of cores in a small space. Hypothetically, if it were orders of magnitude faster than a normal CPU, one could still perform rapid computation on larger numbers as needed while keeping the cpu physically 8 bit- yet be able to revert to even higher performance when less precision is needed.
- spencerflem 2y ago
  If you're interested in One Instruction Computers, check out: https://en.m.wikipedia.org/wiki/One-instruction_set_computer https://en.m.wikipedia.org/wiki/One-instruction_set_computer
  - _yb2s 2y ago
    Thanks! I half expected to be told one instruction computers were impossible.
WorldMaker 2y ago
Just build 4 of them and chain them together to get 64-bits. (Beyond just being a joke, it is often how things like this get scaled. 1-Bit Adders become 2-Bits with a Carry Line between, then 3-bits with another Carry Line, and so forth, ad infinitum and beyond. The real joke is the complexity involved in however you "just" chain them together.)

_yb2s 2y ago

Again, I'm no expert here but find this stuff fascinating. Could the simplicity possibly allow some radically different CPU design that makes the lookups alone nearly instantaneous? I could imagine some types of optical/photonic physical 3D hash table structures - even ones where the same physical structure could support a large number of read operations in parallel if pre-arranged by a compiler to not physically interfere. I imagine a cpu with only one instruction could be physically miniscule, and therefore pack a lot of cores in a small space. Hypothetically, if it were orders of magnitude faster than a normal CPU, one could still perform rapid computation on larger numbers as needed while keeping the cpu physically 8 bit- yet be able to revert to even higher performance when less precision is needed.

spencerflem 2y ago
If you're interested in One Instruction Computers, check out: https://en.m.wikipedia.org/wiki/One-instruction_set_computer https://en.m.wikipedia.org/wiki/One-instruction_set_computer
- _yb2s 2y ago
  Thanks! I half expected to be told one instruction computers were impossible.

WorldMaker 2y ago

Just build 4 of them and chain them together to get 64-bits. (Beyond just being a joke, it is often how things like this get scaled. 1-Bit Adders become 2-Bits with a Carry Line between, then 3-bits with another Carry Line, and so forth, ad infinitum and beyond. The real joke is the complexity involved in however you "just" chain them together.)