Well the odd thing is that if I just use serial (e.g. “hello world” writes) it all works. As soon as I try to set a LED, GPIO or even read mstatus or friends it stops working.
I’ve confirmed that the same program works if I do the override 0x20000000 so I’m wondering if something funny is going on due to what the bootloader does.
I’ll try and get any of those things working with C code to see if I get the same outcome.