I need some advices about overclocking the n900 . With 125/1000 mhz I feel a little lag sometimes , should I increase voltages ? Also , these frequencies are safe ? I don't want to damage the cpu permanently .

Here is the default preset I'm using now .

# DO NOT EDIT THIS FILE - CREATE A COPY OF IT FOR CUSTOMIZATION
# minimum frequency to use
MINFREQ=125
# maximum frequency to use
MAXFREQ=1000
# list of frequency configurations: each "frequency:volt,dsprate"
FREQS="0:20,90 125:25,90 250:38,180 500:30,360 550:54,400 600:60,430 700:60,430 750:60,430 805:60,430 850:60,500 900:60,500 950:60,500 1000:60,500 1100:72,520 1150:72,520"
SMARTREFLEX_VDD1=0
SMARTREFLEX_VDD2=0
GOVERNOR=ondemand
UP_THRESHOLD=95
SAMPLING_RATE=300000
IGNORE_NICE_LOAD=0
POWERSAVE_BIAS=0

No, voltage will have no effect on the speed on the phone. If you still find it lagging after OC'ing, try swappolube and/or custom transition settings.

You can also, if you feel you must, increase the minimum frequency. IF the lag you're experiencing is CPU-bound (i.e. it's because the CPU can't handle something fast enough, not, say, because of SWAP and disk I/O bottlenecks).

Ideally it should still "sleep" at 0mhz when completely unused. The thing is the on-demand governor for the CPU only increases CPU frequency when it's pretty intensely used. So if the current frequency is 125 Mhz, it's not gonna go up tp 250MHz or whatever, until the CPU is 90% busy, or something like that. From there it's not going to go up higher unless CPU is still 90% busy, etc.

Might be more responsive at 500 to 1000 MHz.

Now I put UP_THRESHOLD 75 instead 95 . What about safety with these freqs ?

Yep, up_threshold at 75 should help a bit, at least in some usecases.

Safety... is hard with CPU overclocking.

I'm not an expert, but I'd say, for the time being, unless you're getting spontaneous reboots, you should be okay. Long long term, you might get unlucky and your CPU may wear down because of the overclock - but that's entirely a matter of luck - your CPU may be fine right now and forever at those frequencies, or it may be fine now but develop some fault a year from now. *Shrug* I honestly have no clue.

AND there's the overhead of having to switch among 13 different levels. You could fix it by removing some of the allowed frequencies, like this:

#COPY FOR CUSTOMIZATION:
# minimum frequency to use
MINFREQ=125
# maximum frequency to use
MAXFREQ=1000
# list of frequency configurations: each "frequency:volt,dsprate"
FREQS="0:20,90 125:25,90 250:36,180 500:38,360 750:60,430 1000:60,500"
SMARTREFLEX_VDD1=0
SMARTREFLEX_VDD2=0
GOVERNOR=ondemand
UP_THRESHOLD=75
SAMPLING_RATE=300000
IGNORE_NICE_LOAD=0
POWERSAVE_BIAS=0

Also, putting it straight to 125 is a waste of energy IMO... And in case of reboots, allowing bigger voltages use to be a fix.

I let only 4 levels

FREQS="0:20,90 125:25,90 500:38,360 1000:60,500"

By the way , when the freq goes to 0 ? When the device is locked ?

Do a thread search on the overclocking thread. There were lots of tests, and it came out that the peek efficiency was actually at 500Mhz. That's why most profiles set that as a default.

Tweaking the number of levels, and the speed to change between them, may help if it's the speed of the initial response you care about. If it's general lag though, you may want to look more at what's running system wide.

i am using 250-500-750-1000, the rest of the speeds are unnecessary because when you reach 500 and it thinks it needs 600, but by the time it changes to 600, 600 hits 95% load and it looks for 700 or higher.

only jumping 4 steps, usually stays at 250/500 when no load

and hovers at 750/1000 when browing or running some other tasks

if you are a heavy user who always uses the device, never letting it rest till the battery is flat, then you might want to consider 500-750-1000 or just 500-1000, the device will be much more responsive.

there are also some people who run the device only at 1000 all the time, but i would not recommend this. there might be *some long term effects (* some are running it for months without issues so far)

and as someone pointed out earlier, 125 is useless because somehow it will always go to 250 the moment you unlock. in simpler terms, 125 is just too slow to do anything useful.

also SAMPLING_RATE=300000 means when you launch something, when it realizes it needs to switch to a higher speed, it will need to wait for 300000 before switching = short delay before it goes smoother

but changing SAMPLING_RATE=150000 means it is not only faster to switch to a faster speed when needed also switches back to slower clock faster = immediate speed when it needs it.

and i dont think jump from 500mhz to 550mhz (500:30,360 550:54,400 ) requires such a big jump in voltage from 30 to 54.