Sorry for the stupid question…
RB600 MPC8343E 266/400MHz network CPU means that its processor may work both at 266 and 400 MHz according to computational needs? 
Rgds
no, it means that it can be clocked at different speeds. We ship the boards with 400MHz
Thank you Normis,
might this be applied also to RB532/RB532A? I have both of them…
If yes, how this can be done?
admin@MIKROTIK_CASSISI] /system resource> print
uptime: 53m3s
version: “3.6”
free-memory: 40116kB
total-memory: 62588kB
cpu: “MIPS 4Kc V0.10”
cpu-count: 1
cpu-frequency: 399MHz
cpu-load: 100
free-hdd-space: 89012kB
total-hdd-space: 126976kB
write-sect-since-reboot: 873
write-sect-total: 81079
bad-blocks: 0
[admin@MIKROTIK_CASSISI] /system resource>
[admin@AdiessellePALMI] /system resource> print
uptime: 1h2m5s
version: “3.4”
free-memory: 9588kB
total-memory: 30144kB
cpu: “MIPS 4Kc V0.10”
cpu-count: 1
cpu-frequency: 264MHz
cpu-load: 100
free-hdd-space: 84904kB
total-hdd-space: 126976kB
write-sect-since-reboot: 733
write-sect-total: 65127
bad-blocks: 0
yes. you can actually change the frequency to a higher one if you wish.
thank you Normis, but… how can I change it? 
you can change cpu speed in /system routerboard settings menu if you have routerboard package installed
Thank you Alex,
I’ve done it, but frequency doesn’t change…It seems that I have the same problem described in http://forum.mikrotik.com/t/rb532-333mhz-how/15461/5 … 
you have to do folowing steps:
/system routerboard settings
set cpu-frequency=399MHz
keep-frequency
Shutdown your board and do powercycle (turn off and on power)
Just connect the console to the board and on startup press any key to enter the BIOS - it is possible to change frequency settings there.