So thanks to lots of testing by Pedro Peña across his CoCo collection, SAMx4 now supports 4K and 16K ram sizes (and the extra 16K ram size in the '785).
https://www.6809.org.uk/dragon/samx4/
Pedro's also designed a smaller version of the board, which is in the "rockyhill" branch in the gitlab repository.
He did come across a slight problem in his CoCo 2 during testing which I've noticed also affects my PAL machine: the SAM sits under the keyboard, really close, and the keyboard has a metal backing plate! Means the JTAG pins kinda need to be bent over to clear it, and even some shielding may be required... Maybe I need to get me one of those pogo pin programming cables...
No clearance issues in a Dragon, of course.
One thing that's not been tested yet is the multi-bank support, so it might work in early Dragon 32s with 16 * 16K DRAMs, but I don't know that yet.
Edit: oh yeah here's Pedro's testing video
SAMx4 1.0
Re: SAMx4 1.0
And now 1.2 - lots of work on the build system means you now don't have to touch the ISE GUI. You still need it installed of course, but if you set up your environment as usual, you can just type 'make' in the cpld/ directory and out pops a set of JED (and SVF) variants. BIG ASTERISK: only tested under Linux. GNU Make required.
The ZIP file contains the main variants pre-built now, so if you can get xc3sprog or similar working, you don't need ISE just to program it.
Various fixes too thanks to Stewart testing and spotting an error that the Dragon 64 hid from me...
Oh, and some special non-default build targets that add a few bits to F and implement an X offset register. Fun for all the family! (But as it diverges from actual SAM behaviour, it'll have to go if I end up needing more space for any future fixes).
The ZIP file contains the main variants pre-built now, so if you can get xc3sprog or similar working, you don't need ISE just to program it.
Various fixes too thanks to Stewart testing and spotting an error that the Dragon 64 hid from me...
Oh, and some special non-default build targets that add a few bits to F and implement an X offset register. Fun for all the family! (But as it diverges from actual SAM behaviour, it'll have to go if I end up needing more space for any future fixes).