Re: ibook system bus speed
On Thursday 10 March 2005 12:43, Christophe Branchereau wrote:
> ide: Assuming 33MHz system bus speed for PIO modes; override with idebus=xx
>
> A quick look on google told me that the system bus speed of this model is
> 66MHz, as http://www.apple-history.com specifies.
>
> Isn't it degrading disk performances a lot?
> As the dma mode that was set to 16 Bits by default, for example.
Hmm.. interesting. I've noticed that message on my x86 machine, but I never
spotted it on my iBook. Turns out I have it too. I would have expected the
powermac controller to recognise the ppc laptop models (at least) and to know
what they can handle. Guess not :)
Here's what the kernel driver says on it (leaving out the x86-specific stuff):
"idebus=xx" : inform IDE driver of VESA/PCI bus speed in MHz, where "xx" is
between 20 and 66 inclusive, used when tuning chipset PIO modes. If in
doubt, use idebus=33 for PCI. Bigger values are safer than smaller ones.
Problem is, it says nothing about what actually happens with different
values :(
Worth noting here that you should probably be aiming for DMA rather than PIO,
if your iBook can do DMA IDE transfers.
--
Lee.
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