Messages in this thread | | | Date | Thu, 15 Jan 2004 21:48:48 +0100 | From | Pavel Machek <> | Subject | Re: BIOS Flash changes PowerNOW frequencies? |
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Hi!
> > is "Why?". If the CPU and chipset support both sets of frequencies with > > different BIOS, wouldn't the _real_ set of supported frequencies be the union > > of the 2? > > In reality, yes. > However BIOS programmers have a different perception of reality to the rest of us. > The spec for PST tables allows for up to 256 FID/VID pairs, yet everyone just > seems to offer 5-6 as maximum. I guess they figured no-one needed the granularity > of the full range.
Imagine tests needed to check that hw is stable at each supported frequency. At that point I understand they only support 6 of them...
> Something that has been planned for quite a while has been a means of overriding > the tables using sysfs. I haven't had time to implement this, and no-one else > has found the time/motivation to do so either it seems. >
That would be nice. Both notebooks that I have do have broken PST's... Ouch.
> Something I was tempted to do at one point (due to the number of broken PST's out > there) was to offer a 'ignore_pst' module parameter, which exposed the full table > to sysfs. The only problem being some VRMs can't handle certain frequencies at > certain voltages whilst some can, making it hard to find a set of 'safe' values > for each frequency. > > How to find out which one VRM can handle frequency X at voltage Y ? > Through the PST tables.
Well, you can try it, if it dies, remembed "bad combination" else compile kernel, if it works, it probably is usable combination... at least thats how I did it by hand on k7 notebook. Pavel -- 64 bytes from 195.113.31.123: icmp_seq=28 ttl=51 time=448769.1 ms
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