Thanks, @rhester72.
I came across a few retro computer cores that can be reset by pressing a function key on the keyboard - which is a bit too easy to do. They can all be reset through the F12 menu, it seems to me, so it would be nice if that could be disabled, maybe as an option if people feel strongly they should be able to reset them with one key press.
It seems to me that retro computing is an ideal use for the MiSTer. There are plenty of software based emulators, but re-creating it all in hardware has to be a better choice, and an FPGA is the most convenient way to do that.
I suppose some people would enjoy saving things to a cassette recorder, for the full retro feel, but personally, I'd rather just be able to take a snapshot and put it on the SD card.
One way it could maybe be done with Z80 based computer emulations would be to page in a shadow ROM and use NMI to get the emulated processor to dump its registers and RAM contents to an I/O device, or via a block of memory that would normally be in ROM.
That may seem a little elaborate, but it's how I'd probably try to do it if I was modifying a real ZX Spectrum or Jupiter Ace, and it would save having to redesign how the memory works, to allow it to be dumped. Physically, I suppose the dump should be sent to the ARM HPS memory, for a monitor program to send to a file.