Mostly temperature rise.
Maximum power is dissipated while switching, the higher the frequency, the more power used. Called switching loses.
High speed processors like the Arm have low core voltages to reduce the power dissipated while switching.
Thanks friends. But what will happen if 8085 happen to run at higher frequencies? will it burn? Any other factors decides the maximum frequency of the core? how exactly it differes 8085 and ARM architectures in frequency prespective?
It's called over clocking! A popular pastime with PC's.
Just keep increasing the frequency and run a test program to find the highest stable speed of the micro.