@kernel config show
I suppose it can be fixed if frequency is measured silently before the spike, remembered, and displayed at end. It can even include sleep for 100 msec. But yeah it displays most important info and the value can be measured another way if person know how.

@Overheat
my N900 is warm only while charging (temperature on the back case) so it seems overclocking was going happily. I however wonder why it heats on low cpu usage during charging, because before (KP49 default profile) it was cool (not enogh warm to feel) even after overnight charging. Nothing dangerous (it was warm not hot) but I feel device running while charging run low efficient (it was probably some mechanism fooled because voltage meter is integrated with charging metter, so mechanism got high voltage measured and not fixed input enough). It's rather just high charge usage while charger connected - only a bit decrased device life -mostly battery and charging chip.

@Overclock
after tweaking dosbox a bit (overlay, noscale, fullscreen, byhand cpu limits, big mixer buffer, small sound time buffer) and having good overlocking profile upto 900Mhz I can run Another World (VGA, HQ sound) on dosbox (sound limited to 16khz probing while HQ in AW is 10khz) really smoothly (including intro movie) so both given me important boost, so I perhaps may try win3.11/win95 on dosbox or some more recent dos game (although don't know which one because best dos games have remade engines to native compiled for arm so it's dumb to even install it on dosbox). It seems my N900 is capable of much more than I believed once having KP (overclock, VDD) and tweaking apps settings fair. Thanks pali and guys!

PS: some games lock at max despite were running smooth on 600. Does using such apps with overclock feature reduces my device life in a visble way? Should I write some launcher script to swap profiles before running them and swap back after closing to default?