> Vojtech Pavlik writes:
> > On Mon, Feb 25, 2002 at 09:01:06AM +1100, Paul Mackerras wrote:
> > > We have some RS/6000 machines that have two separate PCI buses (two
> > > host bridges) that run at 33MHz and 50MHz respectively. Fortunately
> > > we also get a device tree from the firmware that tells us this.
> >
> > I really wonder why the 50 MHz one doesn't run at 66 MHz, and what
>
> Apparently the rationale is that you can put more slots on the bus
> if you run it at 50MHz than you can at 66MHz.
I see. That makes sense.
> > happens if you plug in a 66MHz non-capable card to the 50 MHz bus.
>
> The bus speed drops to 33MHz.
Interesting. I'd expect 25 myself ... then we'll definitely need two
clock values in struct pci_bus - because the hi-speed one isn't always a
double the low one - as shown by your example.
-- Vojtech Pavlik SuSE Labs - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/