In my last post I talked about the original Interak and the “new school” variants from the current enthusiast community. This time around I’m going off on a slight tangent, athough it’s adjacent to the subject matter so I hope you’ll forgive me. For a while now, I’ve been thinking how to create a display for a breadboard computer. There’s three approaches out there: Memory mapped I/O based display Serial terminal Memory Mapped Displays The memory used by the video output is shared by the main system; these types of displays were very common in the early microcomputers of the 1980’s.

I’ve been continuing my exploration of the Interak Computer System as part of my effort to emulate it. Emulating this thing is somewhat tricky as there was no real “standard” configuration; the Interak was designed to be hacked on and customised by the owner meaning that there are quite a few bits that can vary. I’ve decided that there’s a few main “targets” for emulation: ZYMON2 (32/64 column) cassette based system DMON (32/64 column) disk based system CP/M (80 column) compact flash based system The first two are “original” ZYMON/DMON-based Interak systems from the 1980’s, the latter is based on the work of the current enthusiast community.

We all remember certain games from our youth. They could be great games, terrible games or just games that spark a particular memory or emotion when you think back to them. Everyone’s list is different, it’s a very personal thing. One such game for me is Cosmic Conquest, originally released as public domain for the Amiga in 1988 by Carl Edman. Cosmic Conquest is a turn based strategy game that pits 4 players against each other fight it out for control over the local space sector of 16 stars.

The Interak Computer System is a Z80-based computer from the early 1980’s that was designed, created and distributed by Greenbank Electronics. The Interak was designed as an expandable system, wherein the user created their desired configuration by building and inserting expansion cards. The target audience of this computer was seemed to be largely educational; either for institutions or for home enthusiasts who wanted to tinker with a computer. Remember, this was in 1982, so we were in the boom period of the British Microcomputer golden age.

This is the third post in a series about building an RC2014 compatible Z80-based machine from scratch. It’s based loosely around the Amstrad CPC 464. In the last post I talked about designing the Z80 Cpu module and the backplane. Clock Module One of the things that a CPU needs to operate is a clock. It’s the thing that ticks through each cycle and makes the CPU does its thing.

This is the second post in a series about building an RC2014 compatible Z80-based machine from scratch. It’s based loosely around the Amstrad CPC 464. In the last post I talked about the breadboard computer I started building in early 2021. I’m loosely calling it “bbz80”, but perhaps I need a snappier name. It’s time to move away from breadboards to end up with something without as many wires! System Overview We’re building an 8-bit computer based on the Z80 CPU.

Some time in late 2020/early 2021 I started a project to build a Z80-based computer on a breadboard. In this post I’ll take a retrospective look at the initial version of the breadboard machine, the motivations for doing it and some of the design considerations. Then we’ll explore the next steps for the project which I am planning on documenting as I go along. Kit computers Making your own 8-bit computer seems to be a bit of a rite of passage for people with an interest in old stuff and electronics.

Recently, I’ve become somewhat intrigued by the Amstrad CPC. It’s a machine I never owned or had any exposure to outside of being about 7 or 8; the only other kid I knew who had any interest in computers showed me a few games on his green screen 464 before remarking that my Spectrum was more colourful. From a technical point of view, the Amstrad CPC 464 is pretty remarkable. 64K of RAM as standard with 2 banks of 16K ROMs built in - and you can page the ROM out to get access to all the RAM underneath.

Image compression in SMEGv2 There’s a few technical differences between SMEG v1 and the current v2 (SMEGCPC) codebase; most of which come about from looking at the original problems in a different way and tackling them without the burden of existing code. One of the “big” ones to talk about is how I am dealing with background images for the scenes. In both versions the “stage” area is 240x128 pixels (or 30x16 char cells).

Out with the Old I recently started messing about with the Amstrad CPC 464 to learn how to code on it. Specifically questions such as “how does the screen ram work?”, “how do I move software sprites?” and “how does input work?” etc. To speed up this I wrote some code to convert some of my early SMEG sprites into CPC pixel format and started plotting them and moving them around.