Two new 8-bit Fast Adder boards

A project log for ECM-16/TTL homebrew computer

16 bit Computer made from ttl logic chips

PavelPavel 02/01/2021 at 19:480 Comments

I decided to start to really build the thing (at least ALU for a moment) -- with 16-bit adder as the first part of it. This adder is quite big and complicated, such that it takes up 2 big boards, each of which dedicated to adding a single byte. The adder requires 44 ttl chips to run, as this is a carry look-ahead one, and needs some additional logic when compared to the simplest ripple-carry adder.

Today the boards were finalized and checked using my handy control panel, and no defects were uncovered.

Following in plans is the soldering of logical operations board, which will provide 3 simultaneous 16-bit outputs: AND(A,B), OR(A,B), XOR(A,B). This board looks easier to solder than adders, as all connections are quite local. Basically it will have 4 identical groups of 4 chips, with no cross-connections.

More general plan:

1 - complete the ALU

2 - make a register file 

3 - integrate RF with ALU, which will be the heart - the main datapath - of the whole machine, the place where number crunching is taking place. This part is planned really well as of now, and no changes will be done to it. The rest of the computer -- memory address circuits and controlling logic is still subject to change.

New boards:

1 - in the process of populating IC sockets with actual chips:

2 - Top and bottom sides of one of completed boards: