I've set out to do something that I've had in my TODO-line for quite some time, get minimig up and running on one of my FPGA dev boards.
The choice of board was between SoCKit and DE0 Nano, and I picked the DE0 Nano since the build times for SoCKit are a lot longer,
and even though the SoCKit board has more suitable peripherals, it's a pain accessing some of them from the FPGA side.
Besides, I got a reason to build some nice extension boards from junk I have laying around
I used https://github.com/rkrajnc/minimig-de1
as a starting point for my efforts.
I've now reached a milestone of being able to boot a kickstart 1.2 on the board,
so I thought it be nice to start sharing my progress from this point onward.
So far, I've wired up a simple VGA resistor ladder to a VGA connector from an old graphics card
and a micro-sd->sd adapter (yes, I meant it when I said junk
Another lacking feature of the DE0 Nano is that there is no SRAM, so the openrisc control cpu core has to share the SDRAM with minimig/tg68k
for it's main memory.
I mapped the upper 16MB of the SDRAM for the openrisc control cpu to use.
Speaking of the openrisc controller, I swapped out the old or1200 core in favor of the much better mor1kx core.
(Ok, I might
be slightly biased here since I'm the co-author of the mor1kx core, but it really is
I enabled the instruction cache on the mor1kx core to avoid hogging the SDRAM on every instruction fetch,
but it's still smaller than the or1200 core ~2400 LUTs vs ~2700 LUTs (and I haven't even disabled everything that's not needed).
Another problem is that the TG68K core is not nearly meeting timing at 114 MHz, I saw some other notes around about this, but this will need attending.
Next up is to wire up some PS/2 ports and continue playing around.
Current work of progress is available at: https://github.com/skristiansson/minimig-de1
I end this post with a 'pics or it didn't happen' of the booted kickstart