My brand new 8-bit computer

[bwat]

Another e-bay purchase, but this time, in contrast to the 4-bit computer, it's a machine that will be able to run a homebrew OS. It's an 8085 based machine with 2KB ROM, 256B RAM, 2x8-bit and 1x6-bit IO ports, timer, keypad, and 2x7-segment displays.



Unfortunately, this is a kit computer and I solder like a programmer. Wish me luck!

This kit actually looks quite good. You basically go through the 14 lessons bootstrapping an 8-bit computer, testing each step of the way to make sure you constructed it properly. The lessons are not going to challenge the majority of you reading this. Personally, I see it as a chance to build my own machine from components that I've always wanted to do but never really got round to doing.

You can check out the manual on-line: http://www.elenco.com/admin_data/pdffiles/MM8000K1.pdf

[qw]

Nice! Success, and have fun!

[bwat]

Built!


This product is definitely aimed at people who want a practical knowledge of computers at the discrete component level. I thoroughly recommend it, especially to some of the beginners on this board who need to learn about assembly code, processor buses, memory, and I/O ports. See the manual by clicking on the link in the first post if you want to know the ins and outs of it all.

Nice! Success, and have fun!

It was great fun. I managed to solder in the lm7805 back to front and had a nightmare trying to desolder it out again! But that was just my rusty construction skills. Another user error where I mistakenly entered 0x62 instead of 0xC2 (which look pretty similar on the LEDs) took three evenings to find. Going through the ROM contents trying to find it nearly killed my fingers. All in all I would definitely do another kit computer as I know find construction quite enjoyable/therapeutic.

[qw]

All right! Next assignment: make a web browser run on it...

[bwat]

All right! Next assignment: make a web browser run on it...

Alread did. Look at the the two 7-segment displays, they've got "OS" on them. Now look at the top of your web browser's window to see the title of the page you're on - what's there - "OS"!!!! Undeniable proof. I was using my mobile phone as a modem but I had to disconnect it to take the picture

[iansjack]

My first computer was a Compukit UK101, built from scratch. http://en.wikipedia.org/wiki/Compukit_UK101

Now that really was a test of soldering skills - even the keyboard consisted of soldering individual push switches to the PCB. Not helped by the fact that one of the ICs was bad. I agonised over whether to pay £100 pounds extra for 8K of RAM instead of the standard 4, but decided I couldn't afford it. When the package arrived it contained 8K and a note reading "Packed by Dave who used to live in Heather Close." - the road that I lived in!

[qw]

All right bwat, you rock! Now make it hack into the NSA's mainframe!

iansjack, that looks like a pretty decent home computer already.

[iansjack]

It was a pretty decent home computer (in the Commodore Pet sense) within the limitations of 8K of RAM. But it had a built-in machine code monitor so could be used in much the same way as development kits (with a lot less hassle). Building something like that certainly puts into perspective the idea that people with a screwdriver, a bunch of components, and half-an-hour to spare are building their own computers - especially when it doesn't work first time. (Luckily the IC that was bad was one that was also used in the cassette interface, so I was able to swap it to confirm the problem. It was only a cheap TTL chip worth about 50p.)

I love building electronic kits, but I've never attempted anything that ambitious again. I hate to think how many soldered joints there were in it. The good thing was that every chip was socketed which made life a bit less fraught.