IOMD version and screen modes on RPCEmu

I was experimenting with color settings on the RISC OS Direct version (5.28) of RPCEMU (0.9.4) to check of !ELS behave and encountered some issues with RISC OS. I also tried the latest 5.29 ROM but it made no difference.

The system reported that it supported 4K, 32K, 64K and 16M in RISC OS 4/Select classical BGR format but for some reason in some resolutions (1280 × 1024 and 1360 × 768) 64K came out messed up and on checking, the system signaled in its mode flags these modes as RGB instead.

I also only got 256 colours in Full-HD thought it should support 8MB of screen memory. Then I noticed the monitor was Acorn AKF92 and changing it to the RISC OS Direct generic one got me the full 16M. I don’t know why the difference, as far as I know, there is no colour/memory info in these MDFs. I also noticed now only Full-HD triggers the 64K problem, not the other resolutions.

Finally I also noticed that the background images often gets its colours wrong when changing between 4K/32K and 64K colours (something assuming no colour changes if the mode uses the same number of bytes as before?).