Alexander Shabarshin of NEDOCON has created the impressive NEDONAND homebrew computer:

NEDONAND is 8-bit homebrew computer entirely built out of many 74F00 chips (2-input NAND gates)

source: https://hackaday.io/project/9795-nedonand-homebrew-computer

source: https://hackaday.io/project/9795-nedonand-homebrew-computer

source: https://hackaday.io/project/9795-nedonand-homebrew-computer

Alexander describes the details on Hackaday.io:

I started NEDONAND in order to achieve a few goals:

•  use only 74F00 chips (2-5 ns delay per gate) to get maximum possible performance (at least 1 million instructions per second)
• 8-bit data, but 4-bit ALU (similar to Z80) with carry/borrow and overflow flags (with approach similar to 6502 where borrow is inverted carry)
• no microcode in ANY form, just 2-stage pipeline and RISC instruction set (similar to PIC – 4 ticks per cycle, 1 cycle per instruction)
• open source (public domain hardware and copylefted software) and hobbyist friendly design (only through-hole components)
• all parts will be well-documented and could be used as standalone addons in other projects
• everything simulated in Logisim first (circuits are provided as a single nedonand.circ file)
• plan to build PC-connected “testbed” to test different parts of the project separately
• If you want to purchase NEDONAND boards (I share only tested ones): OSHPark/Shaos
• Hardware files for Eagle v5.12 and gEDA (pcb): Eagle files, gEDA files (it may have some untested things).

In this video, Alexander shows part of the NEONAND program counter:

Shared Projects on OSH Park by Alexander:

NEDONAND-1