seemingly…
Do you have 2.13 RouterBOOT[BIOS] version ?
What? 533MHz CPU on rb600 ? 
my board is 399MHz config (400 max)
You can overclock the RB600’s to 533mhz. I wouldn’t recommend it for production use though.
/system routerboard settings change-frequency frequency=533MHz
-Gerard
why?
yes
Why?
If I had to guess I’d say it’s possible for it to become unstable under extended operation at that clock speed; especially in a sealed enclosure… Just a guess though.