The Apatco 6502 breadboard computer kit I’ve been building is complete. The next stage was to make it more so. A word of warning, though. This story does not have a happy ending. Nonetheless, someone may find the attempt at debugging entertaining or instructional, so here it is. The kit is sold (or perhaps ‘was’ would be better, as it… Read more »
Now that the Apatco kit is working – at least the basic version (having trouble with the keyboard and display upgrade) – it’s time to mess around with writing code for it. Many people swear by the now-abandoned CC65 as their compiler/assembler of choice for 6502 homebrew computers. But I’m going with Beebasm. Although inspired by and largely aimed at… Read more »
If in doubt, start again. That’s not a real saying, but it should be. As we saw in the last post, the Apatco 6502 breadboard computer was finally wired up but refusing to work. I’d fixed my faulty ROM code, buzzed out all the address and data lines to check they were connected correctly and determined that the reset circuit and… Read more »
Okay, so it was time to deal with something that has been nagging at me for a while. I have this Apatco kit 6502 breadboard computer kit and never quite got around to finishing the basic setup. It takes a lot of wiring. I just got tired, put it in a box and shoved it in the projects cupboard. For… Read more »
My Zolatron 64 homebrew 6502 computer project has stalled of late. But it is high on the list of things to restart once I get current projects out of the way. And a recent development has inspired me to look at it again. If you’ve been here before, you’ll know that my plan was to first build a kit –… Read more »
Things can get a little confusing with the 6502 microprocessor’s clocks. The datasheet details three clock pins which, for the current version of the chip are PHI2, PHI2O and PHI1O. And with older versions of the 6502 you’ll see PHI1 instead of PHI2. As I detailed in a previous post, the situation is actually simpler that it first seems. It… Read more »
The Zolatron 64 6502-based homebrew computer has a 16-bit address bus and I want to be able to interact with it manually. How do we do that? The answer is a front panel with switches and lights, as outlined in the last post. But it’s going to be a bit more complicated than just wiring each line of the bus… Read more »
Any self-respecting retro-style homebrew computer needs two things – switches and blinkenlights. Otherwise, why bother? I haven’t got a working computer yet but already I’m thinking about a front panel for it. This will be inspired, to some extent, by the Altair 8800 and also by the PDP-8, both of which I have in the form of modern replica kits…. Read more »
Sometimes the things that confuse you most turn out to have the simplest solutions – and so it was with the clock for my Zolatron 6502 homebrew computer. First, let’s deal with the 6502’s clock pins. There are three of them and they’re called PHI1O, PHI2 and PHI2O – except when they’re not. Older versions of the 6502 have PHI1… Read more »
Within a couple of hours of posting the schematic for the main board of my Zolatron 6502 homebrew computer the doubts had already started to set in. I made the mistake of visiting Grant Searle’s site. I’m already familiar with his work having built one of his projects (an FPGA-based CP/M computer), and so I know he’s forgotten more than… Read more »
Well, things are finally happening and I actually have a schematic for the main board of the Zolatron 64 6502-based homebrew computer. I’m not saying it’s a good schematic. And I’m certainly not claiming that it will work. But it passes the Electrical Rules Check and I don’t think I’ve missed anything out. So that’s an achievement in itself. Click on… Read more »
In my earlier post on address decoding logic, I mapped out a fairly simple way of dividing up the 64k address space for my 6502-based retro computer. But maybe it was too simple. There is one slight complication – easily fixed, but which will require the introduction of another chip. And the reason for this is something lacking in memory…. Read more »
Having looked at a lot of homebrew computers online, including the popular RC2014, it seemed obvious that the best way of going about my own project is to opt for a backplane design. But maybe it’s too obvious. Just as I was ready to get started with designing the Zolatron 64 I stumbled across this page (via the excellent 6502.org… Read more »
We all have to start somewhere. Almost as soon as I’d decided I would build a 6502-based micro I realised that the learning curve is steep. It’s not like embarking on a new programming language where you can write a ‘Hello world’ program and go from there. When building a computer, there are many pieces that have to come together and… Read more »
Yeah, I know what you’re thinking … he really should get on with building the damn computer. But I have a thing about fonts, so sue me. I was rather pleased with the original Zolatron 64 logo. I chose a font called Eurostyle because it was the most 1970s-looking one on my machine. Then I read about the history of… Read more »