On Sun, May 16, 2004 at 10:28:09PM +0200, Jean Delvare wrote:
> Hi all,
>
[snip]
Another implementation to add to the pool. Note I'm not convinced this
is the best solution, since I know little about the hardware
limitations...
Implementation #5
Since the divider can be programmed, it is possible to take two
measurements (all in the driver): first with the highest divider
allowed by the chipset to get an indication of the current speed, and
then a new measurement followed as close as possible to the first one
with a divider fitting the first measured speed.
Example: set divider to 64 (or highest possible divider); fan speed
gives 2500 +- 500. Not set divider to 2 or 1 and re-measure.
Advantages:
- no 'low limit' has to be set magically
- most accurate reading possible on the whole range
- invisible to the user
Disadvantages:
- no 'low limit' can be set in the hardware; low limit must be
processed in software.
- Update frequency of the fan speed will be halved.
Maybe-problem:
- The 'as close as possible' must be in a small range or otherwise
the fan speed may be dropping to fast to fall outside the
measurable range. I do not know with which frequency the fan speed
can be measured.
Processing the low limit in software will also solve the 'BIOS
triggering false alarms'.
> ### CONCLUSION
>
> I think I'll stick to #2 for now. The extra code is reasonable, and I
> don't really see the low accuracy at high speed as a problem. What
> matters much to me is that the user shouldn't have to worry about
> selecting dividers himself, and #2 does this.
I agree with the stated 'I don't really see the low accuracy at high
speed as a problem', but this would suggest a simple
3-or-so-line-patch to solve the problems: just use the highest fan
divider by default. If a user really knows what he is doing, he can
change the divider himself.
--
Rutger Nijlunsing ---------------------------- rutger ed tux tmfweb nl
never attribute to a conspiracy which can be explained by incompetence
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