Zolatron: 6502 address decoding

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This was something I’d always wondered. When you have data on a bus, how do you ensure it’s read by the device that needs it, and only that device? And when you read data from a device into the microprocessor, how does the processor read data only from that device? What we’re about to embark on here is address decoding…. Read more »

Zolatron 64: starting point

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Having decided to build a 6502 microcomputer, I was immediately successful in overcoming the first hurdle – and possibly one of the most critical stages in the whole project – by coming up with a name for it. It’s the Zolatron – or the Zolatron 64 to be precise, because it will have a total of 64K addressable memory. However, that… Read more »

Building an 8-bit 6502 computer

So I’ve decided to build an 8-bit computer based on the 6502 microprocessor. Because nothing screams ‘success!’ like creating something that was obsolete 30 years ago. The truth is that I got into retro-computing partly because I wanted to understand computers better. Yes, I can code well enough for my needs in Python, Objective-C and Swift using sophisticated frameworks, and… Read more »

AVR basics: interrupts

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I confess I’m really enjoying delving into the secrets of AVR microprocessors. Having used Arduinos for some time now – as well as other AVR-based boards such as the mighty and wonderful Teensy – I came to the conclusion that I’m a master at µcontroller hacking. Working with ‘raw’ AVR processors quickly disabused me of that notion. The Arduino ecosphere shields you from a… Read more »

Next project: drifting off to sleep…

So after I built my wife her dream machine, I got jealous. I too would like to ease my way into sleep. After all, I’ve already built a machine to wake us up gently. So I decided to build my own dream machine. And at first, my plan was to simply make a replica of Trish’s, but loading music rather… Read more »

Beeb down…

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Alas, the reconditioned BBC Master Turbo I bought towards the beginning of last year is now sickly. What was a stroll down memory lane has become a project. When I switch on the machine, I get the Acorn MOS message and (usually) the DFS one, but then only a flashing underline cursor. Once or twice I’ve seen more (‘not a… Read more »

Dumpster diving

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It’s amazing what people throw away. This morning, the More Significant Other and I stopped off at the local dump to drop some things into the charity collection point. And my eye was caught by a bin full of computer monitors. Sitting on top of the Nineties-era Dell and Acer CRTs was something a little more retro-looking. I knew what… Read more »

Simulating days gone by

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The Apple II was never my machine. My 6502-based microcomputer of choice was the BBC Micro. And, to be honest, I think the Apple II was always more of a US phenomenon than a UK one. And yet one can’t escape the fact that it was a hugely significant product in microcomputer history. It made Apple wealthy and famous. It brought… Read more »

So many adventures, all the same

My first contact with Adventure – or Colossal Cave, if you will – was in 1984. I was working on the launch of a magazine for MSX computer users and, to help things along, our innocent publisher had fixed us up with a Telecom Gold account. Aside from providing us with an email account, this also gave us access to online databases… Read more »

A little bit of an obsession

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So I wrote this Python program to allow me to carry out certain kinds of calculations on binary numbers — you know, AND, OR, XOR and that kind of thing. It’s an absolutely essential tool for anyone who, you know, needs to NAND two 12-bit binary numbers. And happens to own a PiDP PDP-8 replica. Okay, so that’s a very… Read more »

Something useful

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If you’re into retro computing, or building stuff based on SBCs such as the Raspberry Pi or BeagleBone, you’ll be familiar with a certain refrain from your significant other and even those you consider your friends. They’ll look at your latest project — perhaps a restoration of a 1980s home micro, or a simulation of a 1960s mini computer, or something… Read more »

Python on the PiDP

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I’m not really a C kind of person. And so when I finished building my PiDP kit, I immediately started thinking, ‘Wouldn’t it be nice to use all these switches and lights from Python?’ Because Python really is my kind of language. You can be properly expressive in it. And there’s not all that nasty business with make files. Fortunately,… Read more »

Networking VAX OpenVMS on SIMH & the Raspberry Pi

[Update 10/03/2017: some broken links were fixed] We’ve already had some fun getting a VAX up and running with OpenVMS under SIMH on a Raspberry Pi. And boy, what a mouthful that is. I’m building my installation on my lovely PiDP just because it seems appropriately retro. I mentioned at the time that the next step would be getting networking… Read more »