alt Hacker NewsNeat to see this on HN after discussing this a bit with you on the Emudev discord (I'm Mask of Destiny there). I'm curious if you tested this on hardware. I think I mentioned this previously, but my understanding is that the SH-2s are incapable of writing to the cartridge area [0]. This would seem to preclude using the cart as RAM even with the extended "SSF2" mapper. Did you find that to be not the case or was this only tested in an emulator?
[0] - See this Spritesmind forum thread https://web.archive.org/web/20190209161834/http://gendev.spr... (Internet Archive link because the live site is mostly unusable due to the scraper deluge)
Hi! Nice to see you here.
Yes so, this was tested within a software context; the ASIC that does the bus arbitration on the side of the 32X has some of the required pins as N/C. They do a much more interesting deep-dive on the link you added.
I initially thought the 68000 side /UWR & /LWR pins were wired to the complimentary 315-5818 ones (Since there wasn't any apparent difference between the pinouts of both).
This makes the setup a bit different since you'd not be addressing the cart's PSRAM, but instead, the 32X's SDRAM. With XIP (Like on the Jaguar port) you could probably pull it off (Not sure if you'd be able to cram the entire Busybox environment but maybe a small program could do it).
Good thing is, this is actual Linux (And not uCLinux) so there's still stuff that can be disabled further if for some reason it can't fit still on the available memory.