On Fri, Nov 14, 2003 at 12:21:30AM +0100, Manuel Bouyer wrote:
> On Thu, Nov 13, 2003 at 03:14:25PM -0800, collver1@comcast.net wrote:
> > Hello,
> > 
> > I have read that the standard PCI bus can be clocked at 20 to 33MHz, and
> > the specification provides for it being clocked at 66MHz.  It appears I can
> > find whether a device is going 66MHz in NetBSD.  In my computer it appears
> > my on-board IDE is going at 33MHz and AGP is going at 66MHz.
> > 
> > $ pcictl /dev/pci0 dump -b 000 -d 01 -f 0 | grep -e Device -e 66
> >     Device Name: 82845G/GL Host-to-AGP Bridge (0x2561)
> >       66 MHz capable: on
> > 
> > $ pcictl /dev/pci0 dump -b 000 -d 31 -f 1 | grep -e Device -e 66
> >     Device Name: 82801DB IDE Controller (UltraATA/100) (0x24cb)
> >       66 MHz capable: off
> > 
> > Is there any other way to detect the PCI bus timing on a typical PC?
> 
> Unfortunably no

Also (IIRC), for a PCI bus to run at 66MHz all the devices on the bus
have to support 66MHz.

> > How common is it for a PCI bus to be timed slower than 33MHz?
> 
> Overclocked systems, and older Pentium/pentium pro with a speed multiple
> of 25 or 30 Mhz instead of 33 (e.g. 180Mhz vs 200).

Or a P75 we had which actually ran slightly below 25MHz - causing problems
with a certain 100M ethernet card which expected the PCI bus to be faster
than its own 25MHz crystal...

	David

-- 
David Laight: david@l8s.co.uk