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> <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. -- :!mcr!: | The postmaster never | - Pay attention only Michael Richardson | resolves twice. | to _MY_ opinions. - HOME: mcr@sandelman.ocunix.on.ca + Small Ottawa nodes contact me Bell: (613) 237-5629 + about joining ocunix.on.ca!