A busy weekend!

A project log for rosco_m68k

A full-featured Motorola 68k retro computer, starring a 68010 running at 8MHz

Ross BamfordRoss Bamford 04/11/2020 at 22:200 Comments

So, I'm having a busy weekend here, having just launched the rosco_m68k on Tindie I've spent some time putting together my first few orders (thanks all who've ordered so far!) but luckily I've still found plenty of time for hardware hacking. 

I've been busy working on the first expansion board for the computer, which is going to be a RAM expansion. I'm thinking of making it configurable for either one or two MB of expansion RAM, and where it maps into RAM will be configured by jumpers. The prototype is mostly working great:

In this picture it's still using a couple of 7400-series ICs for address decoding, but I'm replacing them with an ATF16V8BQL which will make it easier to support the jumper configuration and such and will save space when this thing becomes a PCB. I'm probably also going to make a simple bus-board to break the expansion bus out to multiple connectors. I feel like doing that now, and making the first expansion compatible with it will save frustration later.

Speaking of the 16V8 I've finally bitten the bullet and converted the WinCUPL code for the address decoder and IO glue to GALasm (not the original link, but the one I used). I've been meaning to do this for a while, because WinCUPL just deeply and severely sucks, and it only runs on Windows (as you might have guessed from the name) but because I've not really done anything with the CUPL since I first wrote it, I've just kept putting it off - it's good that I've finally had need to make some changes and do some new GAL code as it's spurred me on to finally do the conversion.

I've not added GALasm to the Home-brew tap I created to house to m68k GCC toolchain, because I figure that most people will want to recompile the GAL code (I include the Jedec files in Git anyway) so it would just add bloat...

While I was busy working on the RAM expansion, these turned up:

So it looks like I'm going to be ever busier than I expected I would be this weekend. I can't wait to get started with these but I don't have the breadboard adapters back from JLC yet (these are shrink DIP packages), and in any event I want to finish off the RAM expansion so these will have to wait a day or two :)