[MiNT] New MiNT updates

[Joerg_Westheide@su.maus.de (Jörg Westheide)]

Hi Martin!

MER>DMA - Direct Memory Access:  a functionality which allows peripherals
MER>to buffer their operations into system memory, without passing
MER>through the kernel's memory management (the kernel is simply notified
MER>if/when a peripheral is currently accessing a memory zone - that's
MER>all).
Well...
DMA - Direct Memory Access:
Data can be transfered between memory and a periperal without the processor

Background DMA:
Means that the processor continues to execute processes while a DMA transfer
is running

MER>The problem in performing Background DMA is that the operation will
MER>happen completely without the kernel's intervention; we must bypass
MER>it and directly access memory zones whose management is yet still
MER>under the kernel's control, for normal operations.  This goes beyond
MER>simply forking the disk-access routines.
Currently MiNT initiates a DMA transfer and then waits for it's completition
(so the execution of processes is blocked while the transfer is taking
place). With Background DMA the kernel has to take care about some things
while the transfer is running:
- not to access the memory accessed by the transfer
- not to start a new transfer while the current one is not finished
(may be that I forgot something)

Bye

                Joerg