Re: [PATCH] - Initial dothan speedstep support

[Michael Clark <michael@metaparadigm.com>]

On 08/22/04 15:31, Clark, Michael wrote:
>>Hi!
>>
>>
>>>So here's a patch on top of the above patch that adds all of the
>>>dothan frequency/voltages for processors 715, 725, 735, 745, 755
>>>
>>>Tested and working as it should so far with a 745. The stepping in the
>>>model table for the others may need to be tweaked.
>>>
>>>The Dothan processor datasheet 30218903.pdf defines 4 voltages for
>>>each frequency (VID#A through VID#D) whereas Banias only suggests a
>>>typical voltage and no min or max for each freq so i've used the OP
>>>macro to allow definition of all voltages (A through D) but the macro
>>>currently just uses VID#C at compile time (the second lowest voltage
>>>profile).
>>
>>I thought that whether to use VID#A, B, C or D depends on
>>your concrete chip? Not all chips are certified to run on VID#C...
> 
> 
> Yes, I believe this is the case. When I read the processor spec
> document it did not mention this but since then i found this out. I've
> since changed the patch to use the VID#A voltages which is more
> conservative (assuming that all of them will run at the higher voltage
> okay which according to the upper voltage rating of 1.6 volts might be

On re-looking at the spec and the voltage tolerance tables in particular
I realize my approach is not valid. A VID#B can be driven at VID#A
voltages but there is no voltage in common for some frequencies between
all VID# variants.

> okay). It would of course be preferrable to work out the the type
> VID#A,B,C,D via software - not sure if this is possible.

Perhaps the VID# variant can be found via MSRs - if not the static tables
will not be workable and the ACPI approach will have to be the sole method.

~mc