On Friday 18 March 2005 11:20, Timothy Miller wrote: > On Thu, 17 Mar 2005 21:47:59 -0500, Daniel Phillips <[EMAIL PROTECTED]> wrote: > > On Thursday 17 March 2005 18:45, Attila Kinali wrote: > > > On Thu, 17 Mar 2005 17:27:04 -0500 > > > > > > Daniel Phillips <[EMAIL PROTECTED]> wrote: > > > > Next question: is 32 bits of hardware DMA address enough? That > > > > handles up to 16 Gigabytes physical memory (assuming 4 byte > > > > alignment) without having to resort to sickening hacks. Believe > > > > it or not, 16 GB is commonly thought to be insufficient these days. > > > > > > If we limit our selfs to 32bit pci, then it's enough, > > > but 64 bit is around and is used. Also note that our > > > cards own memory could be at any place in a 64 bit adress range. > > > So, i'd say to save us and the driver writers head aches, go > > > for 64 bit. > > > > Timothy answered that: 40 bits is the number. That is a good choice, > > and also fairly typical. > > The example I gave was bogus. I included only one address, while a > DMA memory-move command needs both a source and dest address. We need > more words in the command packet. Three should do it.
Hey, I thought you were just being insightful :-) The on-card destination address is a one-time setting, followed by potentially a whole bunch of 4K transfers to implement the scatter/gather. So 8 bytes really is the right number, plus an 8 byte destination setup command. Regards, Daniel _______________________________________________ Open-graphics mailing list [email protected] http://lists.duskglow.com/mailman/listinfo/open-graphics List service provided by Duskglow Consulting, LLC (www.duskglow.com)
