In part one of this series we explored the Z80 processor and found out what various pins do. And we explored a few of the Z80s opcodes by manually feeding them into the data pins. But feeding instructions and data in manually is hard work. We need to add some memory so we can feed …. Read More
Many people are learning, like I did, about computer hardware by following Ben Eater’s 8-bit breadboard computer build. And many of those are either moving on to more advanced projects or using slightly different hardware for the build. And some of those are using larger EEPROM chips such as the 28C256. But there’s a catch …. Read More
A lot of people build Z80 based computers. They build something with some flashing LEDs, some buttons, and maybe even a serial port. But the computers I loved as a kid had high-resolution displays, and keyboards, and joysticks attached. And you could spend your days playing games on them. So, I’m going to attempt to …. Read More
I’ve been breadboarding a Z80 computer lately. I wanted a test bed to explore ideas and to learn how the hardware worked. I also wanted to be able to create a small, self contained Z80 machine including both input and output devices. The simplest output device to connect is probably a generic character LCD display. …. Read More
The One Where I Show How-It-Works And How To ‘Burn’ Data To The ‘ROM’ (If you want the source code without the waffle here’s the repository). I recently upgraded my RC2014 to use the 512K ROM 512K RAM board available on Tindie). Most people use this board to run RomWbW but I have different plans …. Read More
My Bentium Pro computer is a Ben Eater inspired machine which uses many of the same ideas and many identical or very similar circuits. My intention with these blog posts was to write about the things I have added or done differently and leave the same/similar stuff for people to copy from Ben. I also …. Read More
After giving you a general tour of the ALU of the Bentium Pro and the carry select circuitry I want to move onto describing the flags register and how the flags are evaluated. As a reminder, the Bentium Pro has four flags: Carry. This can contain the carry/borrow from the adder and also the bit …. Read More
I was thinking recently about OR gates. We normally do these with TTL logic chips but I wondered whether it would be possible to do the same thing with diodes. A quick Google showed that this was not merely a workable idea but something which has a name – ‘diode logic‘ – and which has …. Read More
The ALU on Ben Eater’s original Bentium 8-bit computer has two operations: add (ADD) and subtract (SUB). This gives his design the ability to add and subtract 8-bit numbers. But if you want to add or subtract larger numbers then you need more than 8 bits. You could do this by expanding to a 16-bit …. Read More
Last year I built Ben Eater’s 8-bit breadboard computer, which taught me a lot about how processors work. But with only 16 bytes of memory it’s not really usable for any kind of real world tasks. As soon as I’d finished it I knew I wanted to make some upgrades. And when I looked at …. Read More