OSWORD &FE (254) - Z80 MFM disk read (Z80 Tube OS)
On entry: XY?0 =(send block length) XY?1 =(receive block length) XY!2 =
This is loaded by the Z80 Tube v2 client code from $.CPM.X or $.CPM.Y on the host filing system. The code is currently being disassembled.
OSWORD &FE (254) - DOS Text output (80x86 DOS, unimplemented)
The 6502 host support code in 6502.SYS installed by the 80x86 DOS just returns from OSWORD &FE.