Funny that the boot prom had to do such strange things
to interface
to the 'most intelligent' controller (MSCP), whereas all the other
dumb controllers (RK05, etc) used really simple boot code sequences.
My guess would be that the smarter controller also demanded more smarts
from the host-side software. (I've seen (specs
for) Ethernet
interfaces, for example, that simply can't work without not only
DMA
but a real ring of receive buffers - not a big deal for a real kernel,
but a pain for standalone code like booters, and quite possibly fatal
for severely-size-limited standalone code.)
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