On 8/29/06, Lourens Veen <[EMAIL PROTECTED]> wrote:
How are we on hogging the PCI bus? Are the low-latency Linux people (you know, the ones who build digital audio workstations and hard disc recorders and hack on Ardour and Jack and LADSPA) going to complain about us messing up the latency to their PCI sound cards?
One of the major complaints in the past came from this: Most graphics chips have a way to "throttle" the bus when writing to the drawing engine. That is, if you don't check the command queue to make sure there's room in it and just go ahead and write commands, that's "okay" because the GPU will tell the PCI bus to wait. Some driver developers took advantage of this to get a few % more performance, but the wait periods on the PCI bus got to be so long that other devices were not able to use the bus to service interrupts. OGA simply will not provide a mechanism to throttle the bus when using PIO to write to the command queue, instead, you'll get an undefined result. We discourae the use of PIO anyhow. The second way we can hog the bus is to do long DMA bursts. In the interest of fairness, we'll always limit our bursts to reasonable lengths of time (16 or 32 words, IIRC). _______________________________________________ Open-graphics mailing list [email protected] http://lists.duskglow.com/mailman/listinfo/open-graphics List service provided by Duskglow Consulting, LLC (www.duskglow.com)
