So, you may well remember that I entered Retro Challenge 18 months ago, and what a fun crazy busy time that was! Well, the January Retro Challenge competition is about to kick off in just over 2 weeks. If you're not familiar with Retro Challenge, shame on you! But you can de-shame yourself by heading over to http://www.retrochallenge.org/ and seeing what it's all about. Essentially, it's a month long bi-annual competition where the entrants set themselves a goal based around old school computing and blog, tweet and share their experiences. The goals are pretty loose, as long as they are based on something from last centuary (modern emulators of old kit is fine). The challenge I set myself was to take a breadboard based Z80 computer and bring it to life in modular PCB form in such a way that I could spell out my name on. Have a look back through my blog to see how I did. Spoiler ---->
So, before I dive in to this, a quick history lesson for those of you that aren't fully up to speed on your rare 80's vintage 8 bit computers. In the beginning, there was Clive Sinclair, and he invented the Sinclair ZX80. From the ZX80, the ZX81 and indeed home computing was born. From the ZX81 came the ZX Spectrum. Ok, so Clive didn't invent these single handed. He had a team working for him, which included Steven Vickers and Richard Altwasser. Somewhere between the initial design of the ZX Spectrum and its launch, Vickers and Altwasser thought there was a better way to do things, and left to set up their own computer company. Jupiter Cantab was formed in 1982, and Vickers and Altwasser developed the Jupiter ACE. This little computer was a weird mix of ZX80 (vacuum formed white case), ZX81 (black & white low res graphics, 3k memory) and ZX Spectrum (rubber keyboard, small speaker). The one fundamental difference, however, was that it used FORTH instead of BASIC as it's operating system. FORTH was much more efficient than BASIC, and would revolutionise the home computer market... Although history tells us it didn't. Cantab went bust after 18 months and was bought by Boldfield Computing, who went on to sell off the remaining hardware in 1985. Approximately 8000 units were manufactured. When I was offered an original unpopulated Jupiter ACE by John Fletcher, it was too good to turn down...
Yesterday this tweet appeared on my Twitter timeline [embedTweet url="538666941335236610"] Now, being the geeky retro Sinclair fanboy I am, I read it, understood it, and retweeted it. Obviously.
My original plan had never been to design and build my own computer. I had, however, planned to build a clone of the Sinclair ZX80, which has been on my bucket list of things to own for year, and which I had found plans for online. Whilst collecting the parts and reading up on simple Z80 computers I got kind of sidetracked and ended up with the RC2014. The heart of the RC2014 is a Zilog Z80 CPU, which is the same one that Sinclair used in the ZX80, ZX81, ZX Spectrum and Z88. If the ZX81 and ZX Spectrum can run a ZX Printer, then surely it follows that the RC2014 will be able to too?
just a quick update about my Z80 development environment. If you look down a couple of blogs, you'll see that I found an online Z80 emulator and I'd written a couple of bits that executed in it, so I was going to do my Z80 learning and development on that. However, there were two issues. The first being that it didn't run on Chrome on my Linux PC at home (but did on Chrome on Windows at work). The second issue is that it isn't a Z80 emulator, it's a 8080 emulator. I didn't think this would be a problem as they pretty much run the same instruction set, although the 8080 has a sub-set of the Z80 (well, technically, as the 8080 came first, the Z80 has an expanded instruction set), and I quite quickly came across an instruction that wasn't supported. Bugger! That's messed up that plan. Then I remembered I have Fuse which is a ZX Spectrum emulator running on my Linux PC. There are oodles of menus and options which I've never looked at, but thought it worth a poke (no pun intended) about with.
So, if I'm going to write my name on a bunch of 8x8 LED matrix displays, I have a couple of options; Write my name on grid paper, colour in the squares, convert it to binary and transpose it to hexadecimal. Or... I could use a font that's already out there. Like the one that Sinclair used in the ZX Spectrum. I've already got a copy of the Spectrum ROM, and, handily enough, all the characters are right at the very last part of the ROM address space (from 0x3D00 to 03FF), in consecutive blocks of 8 bytes. I can see this coming in handy later!
Back in July 2013, someone in the office mentioned the beautiful iconic 80's disaster that is the Sinclair C5. Inevitably someone asked what they're worth now, and apart from the fact they cost £400 new, was dropped to £199 shortly after and then the price plummeted like a stone, I had no idea. So I turned to the reliable font of knowledge in these things; eBay. Generally, they were going for more than I expected, then I came across this sorry little thing With 4 days to go, the price seemed far too low, despite it being described as "Spares or repair", so, just for curiosity sake, I decided to watch the auction. With 15 minutes to go the price was still too low, so I bid a stupidly low price... and was the highest bidder! But with 2 minutes to go, I got outbid! Well, the eBay red mist had descended, and I wasn't having any of that, so I bid again... and won it for £34.56! What the hell was I going to do now?
Jupiter Cantab was formed in 1982, and Vickers and Altwasser developed the Jupiter ACE. This little computer was a weird mix of ZX80 (vacuum formed white case), ZX81 (black & white low res graphics, 3k memory) and ZX Spectrum (rubber keyboard, small speaker). The one fundamental difference, however, was that it used FORTH instead of BASIC as it's operating system. FORTH was much more efficient than BASIC, and would revolutionise the home computer market... Although history tells us it didn't. Cantab went bust after 18 months and was bought by Boldfield Computing, who went on to sell off the remaining hardware in 1985. Approximately 8000 units were manufactured. When I was offered an original unpopulated Jupiter ACE by John Fletcher, it was too good to turn down...
.JPG)
