Newsgroups: comp.sys.amiga.programmer
Path: utzoo!utgpu!cunews!micor!latour!mcr
From: mcr@Sandelman.OCUnix.On.Ca (Michael Richardson)
Subject: Re: Virtual Memory Program?
Message-ID: <1991Mar12.055922.27355@Sandelman.OCUnix.On.Ca>
Organization: Sandelman Software Works, Debugging Department, Ottawa, ON
References: <1986@public.BTR.COM> <efeustel.668096462@tiger1> <29018.27db6cde@kuhub.cc.ukans.edu>
Date: Tue, 12 Mar 1991 05:59:22 GMT

In article <29018.27db6cde@kuhub.cc.ukans.edu> markv@kuhub.cc.ukans.edu writes:
>impossible for the DMA to use virtual addresses.  So the OS would have
>to supply translated physical addresses, and would have to lock the
>page in RAM.  The only catch is that the max single DMA transfer would
>be the page size, which on most systems is 4K or 8K, so you would lose
>a lot of the potential performance of DMA.  Unless of course the OS or
>program somehow maintained special buffer areas that were physically
>contiguous.  All these problems makes controllers like the GVP that
>use a shared RAM buffer a bit more attactive.

  Not really. It just makes programmable controllers that do DMA even
better. Good DMA controllers can do scatter/gather operations and take
a list of buffers to which they should move the data.


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