For test, I installed MOS 3.16 on PM G5 with ATI X1900GT
But during/after installation the graphics slow down more than in the demo version and some artifacts appear.
Version 3.15 behaves the same way.
So, no Morphos on G5 for me yet :(

Debuglog:

50.798| smu_init: found keylargo base at 0xd7f37000
50.798| smu_setup_timer: timer UNIT_MICROHZ opened
50.798| smu_init: smucmdbuff allocated at 0x1400f600
50.798| smu_init: smucmdbuff_phys is 0x1400f600
50.798| smu_init: SMU core int installed
50.798| smu_init: SMU doorbell int installed
50.798| smu_init: pgmswitch int installed
50.798| smu_intcode3: programmers switch (ResBase 0x14014900)
50.798| smu_intcode2: doorbell (ResBase 0x14014900)
50.798| smu_intcode1: core (ResBase 0x14014900)
52.551| Radeon: Don't know how to initialise the memory controller of this Radeon
52.551| Radeon: Memory size adjusted to 128MB