The biggest improvement now would be getting the ipu working.
Once I've ported MAME4ALL v2.0, getting the IPU working is my number one priority.
Nice to see you have interest in this device
Can you port your mame emus first?
Yep, I also got an RZX-50 about a month ago and it suffers from similar issues. No IPU support.
It has a jz4755 which is quite a bit more advance than the jz4720 - jz4740 CPUS in the IPU department.
One of the issues with the jz4720 - jz4740 range is that they only work with physical hardware addresses, that is the source image and the destination images must be specified as physical memory.
Linux works with virtual paged memory - you may be able to malloc chunks of memory but believe it or not there is no guarantee that it's contiguous. A chunk of memory that is larger than the pagesize (typically 4096 bytes) can be physically scattered throughout memory. The MMU looks after everything behind the scenes with page mapping so to the user process it appears contiguous but in reality it's probably not.
Anyway, the jz4755 and above looks like it supports paging modes which may be useful - making it possibly more accessible for user space programs. I'll see how this goes. More info on this mode would be great if anyone knows.
Also as another bonus, jz4755+ should be able to do RGB -> RGB type conversions. The jz4755_pm.pdf seems to say it does anyway, though it's implementation isn't that handy.
I've yet to look through the jz4760_pm.pdf but will do so soon.