idebus=133 ?

Dave Ray g4tinker at
Tue Oct 23 04:11:06 EST 2001

Ben and Tom,

Thanks for the replies. The reason I ask is that when
I use "idebus=66" in the boot argument, the syslog
shows bootup message "using 66MHz bus speed.." rather
than "assuming 33MHz bus speed..". So I assumed the
inclusion of the boot argument sped up the computer.
Are the appearances of these messages in the syslog
fictitious? Or should I simply not go over 66?


--- Benjamin Herrenschmidt <benh at>
> >
> >It's my understanding the Mac G4 towers run at a
> bus
> >speed of 133 MHz. However the kernel argument for
> >idebus=xx apparently only allows values up to 66.
> Is
> >this intentional?
> I don't think this value has any meaning on macs.
> It's
> related to the IDE bus frequency, which is 66Mhz on
> Apple "UDMA capable" HW and 33 on older chipsets,
> but
> the ide-pmac.c code does all the calculations
> internally
> and shouldn't rely on the generic idebus value.

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