[OpenBIOS] [PATCH] PPC: Add "real" CPU timebase-frequency override NVRAM variable

Mark Cave-Ayland mark.cave-ayland at ilande.co.uk
Sat Jun 29 15:14:30 CEST 2013

On 29/06/13 14:04, Alexander Graf wrote:

> Am 29.06.2013 um 13:27 schrieb Mark Cave-Ayland<mark.cave-ayland at ilande.co.uk>:
>> Some older OS (particularly Darwin) will get stuck in a timing loop upon
>> boot if the CPU clock-frequency and timebase-frequency aren't set close
>> enough to "real" values.
>> The clock-frequency property is already fairly realistic, so create a new
>> boolean NVRAM variable "force-real-tbfreq?" which when set to true will
>> override the timebase-frequency value supplied by QEMU/KVM with that similar
>> to a real Mac.
>> Hence it is possible to boot these old OS from QEMU by adding the following
>> to the QEMU command line: -prom-env 'force-real-tbfreq?=true' (although of
>> course the guest timing may be inaccurate).
>> Signed-off-by: Mark Cave-Ayland<mark.cave-ayland at ilande.co.uk>
>> CC: Alexander Graf<agraf at csgraf.de>
> I think I'd prefer a QEMU option to modify the timebase for real. That would change the emulated frequency as well as the one it exposes to OpenBIOS.

Hmmm okay - that's something that's reasonably beyond my level of QEMU 
knowledge to do at the moment :/  Although I have seen that some patches 
for throttling QEMU in the past have been rejected...



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