This is my build of Ben Eater's 8-bit breadboard computer. Posted videos of my Build. https://www.youtube.com/channel/UCy30KFB296CIdccvAtxhpkA
Ben Eater's 8 Bit computer videos. Building an 8-bit breadboard computer! https://www.youtube.com/playlist?list=PLowKtXNTBypGqImE405J2565dvjafglHU
Ben Eater SAP 8-bit computer diagram 4-9-2017.vsd This is a MS Office Visio file (.vsd). You can get a Visio viewer if you don't have Visio. I included an XPS file format as well. Using the Visio file you will find it helpful when building it as you can highlight a connection line and it will show you the two connection points.
List of Issues encounter building the computer
Adder Circuit 3-10-2017 ( Reversed Data Lines )
Clock Circuit 3-13-2017 (1 MEG Resistor connected to 5v not Ground)
Clock Circuit – Debounce adjustment need .5 second delay ( 1uf x 470K = 470ms)
MAR MI Address Lines reversed
PC – Added Clear Signal
OP Code – Reset was tide to HIGH Causing count to 7 not 5
Added Reset Buttons
RI needs to be High to Write to RAM, Since a NAND gate inverts the signal w/Clock
Corrected Jump Circuit Only One Nand gate IC ( 4 Nand Gates Used)
Fixed RAM Write issue - Needed to isolate the clock from the RC circuit. Fixed feedback noise.
Added 10K Resistor to Write button in Program Mode (Pull-up to 5 v instead of Floating)
Added RC Circuit to absorb spikes during switching between Run and Program mode. (Not in Picture but in Diagram) This Fixed issue where switching between Run and Program mode caused Memory Write signal to go low clearing RAM contents.