My goal is a 4-bit CPU using recycled cardboard substrate and Diode Transistor Logic. This will develop into an educational platform for me. Attempt to build a four bit computer using recycled, re-purposed and just plain junk as the main construction material. Why? Well, the cardboard is free as my workplace puts it in the dumpster and I do not have the funds to buy better material. A very green build indeed. The first electronic parts to start this were given to me by a friend who passed away and what better tribute than to build a computer. Except for the ALU all gates are either NAND or Nor using DTL. The transistors used are NPN 2N2222 type or PNP 2N3906. Thanks to Yann Guidon and Jezz - Morning Star for additional parts. Very large construction is employed as to aid in my learning about logic circuits and also to make it easier to make changes as I find out what does not work. Each gate measures about 0.75 X 1.75 inches on cardboard cutouts. RISC will used and the clock speed will be very slow at about 3Hz to start. The main bus is 8-bits ( 4 for data and 4 for address ). “