Erwin Rol wrote:
>
>
> Hello All,
>
> I am working on/with RTAI/RT-Linux for a while now in combination
> with XFree 4.0.1 and have some problems that are maybe X related.
>
> For the ones that don't know RTAI/RT-Linux it is an layer between the
> hardware and the Linux kernel. The linux kernel never disables
> interrupts
> with the cli/sti instructions but uses a software implemented version.
> That
> way the layer between the linux kernel and the hardware kan preempt the
> total
> linux kernel for hardrealtime tasks and ISR's. The latency for those
> hardrealtime
> tasks is in the range 5-30usec which is about the best PC hardware can
> give (for
> more info on this see www.rtai.org and www.rtlinux.org)
>
> Now the problem i and a few other developers have seen is that with
> XFree 4.0.x
> the latency gets unpredicatable. On of the causes is the use of cli/sti
> intructions
> in the X server. But after removing those the problem didn't go away.
> Wath i noticed was latency upto 50msec more than 10 times as much than
> acceptable.
> This went away by disableing acceleration on my s3virge DX clone card.
> Someone
> else had simmulair problems with NVidia drivers.
>
> After talking to some other developers the looking for an answer goes in
> the direction
> of a PCI bus lockup of somekind (but 50msec long delay, the 100-200usec
> that the person
> with the NVidia AGP card saw could be explained by that). And why only
> when using acceleration ?
>
> So my question, does anybody know what in the s3virge driver could cause
> a latency of
> 10-50msec for hardware interupts to be handled (hardware info see below)
> ? And why does
> this not happen when acceleration is turned off ?
>
> TIA,
> Erwin
>
Possibly the accelerator is using the PCI bus for a graphics operation.
Have you tried the following:
- Remove any IRQ assigned to your video card in the BIOS setup (though I
doubt this is really an issue.)
- Try "pci_burst" "off" in the XF86Config file Device section.
- Try "pci_burst" and "pci_retry" in the Device section. (Both on.)
- Not running X on a RT system. ;-)
Kevin
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