HP hex displays – cosmic?

HP hex displays - cosmic?
I bought some HP 4N54 hexadecimal displays some time ago at a surplus store. I plugged them into my breadboard just to check them and they all worked fine so I will use them as my debug displays when I start construction. This device fits the purpose very well for a couple of reasons. First ...

More on microcode sequencing

More on microcode sequencing
It’s been a long time since I last posted on this site or did anything¬†related to the¬†project. Way too long. My paying job has had me extremely busy lately. Add to this a long awaited apartment flip we had, sooner than expected due to our contractor’s change of schedules and you’ve got the story. I ...

Thoughts on microcode sequencing 2

Thoughts on microcode sequencing
Back from a 3-week long vacation in Cuba. Time to get back to work. As mentioned before, the machine will be a typical CISC with a wide microcode word, with little encoding. That means that bits from microcode ROM will be directly used as control signals. This is in contrast to a RISC-like approach, where ...

Playing with 74LS181, a DIP-switch and some LEDs 9

Playing with 74LS181, a DIP-switch and some LEDs
I will be using 74LS181 ICs for my 16-bit ALU and I bought some today in a local hobby store. I decided to give a try with this little breadboard setup. It’s not really a CPU but it was fun. The inputs are set by the DIP switch. Switches 1-4 set the A input and ...

Instruction set

I mentioned in my last post that my intention is to design with a two-address instruction set. This means that my instructions will have zero, one or two operands. There is no important reason for this. I am familiar with 6502 (accumulator, one-address) and x86 instruction sets, and I am more used to the latter, ...

Kickoff

This site was set up to document my attempts to build a fully-featured, self-contained microcomputer using only basic logic elements (74-series TTL). The idea itself is nothing new and projects like this one are already out there (and completed – check my links page to see Bill Buzbee’s or Steve Chamberlin’s masterpieces which inspired me ...