[ltp] CPU Idle and whine

[Richard Neill]

Dear All,

I noticed that there is a faint(*) whine audible through the speakers of 
the Thinkpad. It only occurs when the system is idle, so I think it is 
caused by the CPU idle state [kernel 2.6,ACPI].

My current "cure" for this is to run `nice -n 19 yes > /dev/null`
so that the CPU never becomes idle and the noise doesn't occur.

Of course that is not a good permanent solution! Furthermore, it uses 
lots of power (not really a problem when on mains) and makes the CPU hot 
(turning on the fan, which is noisy).

Is there a better solution?

(*)It really is quite faint (thinkpads are good quality machines!) - 
only really audible with headphones (or an external amp), and with the 
volume levels turned up high. It's at 1kHz though, so I'd prefer to be 
rid of it!

Thanks very much for your help,

Richard


P.S. Anyone else trying to squeeze max audio quality from the Thinkpad - 
do play carefully with all the levels. gnome-alsamixer is probably the 
most helpful mixer to see what's happening. Eg switch off any channels 
you don't need, and, I found the 3D control should be on, but the slider 
at 0%. Turn the software mixers up (about 90%), but the main hardware 
volume down - this increases signal-noise ratio. You can make quite an 
improvement in hiss and whine!