Pre hotfix5 overclocking and overvolting to go even higher with OPP voltage levels, was achieved with a script that Jdbye wrote to replace the default op_cpu_speed.sh file. Under HF5 its within the system settings menu's and you set the limits via a GUI rather than editing the script.
You want to walk before you run though and get the Pandora running fine for normal apps and more basic games etc before you see how far it will go. Otherwise you wont know whats an OC caused problem or not, not because its dangerous.
N64 emulation benefits from a default speed of about 800mhz and frame skip settings of 2, whilst PSX can benefit some games with alot higher than that, if your individual Pandora can achieve high speeds without locking up. Worse case scenario is a reboot or having to leave the battery out for a short time to re-enable further attempts at OC'ing at a lower level.
Lifespan overall is reduced from 10 to about 5 years in the theoretical scenario of running at 1ghz permanently for that duration according to TI chip specs, or something similar.
Best bet is to alter the settings to allow for the cpu slider to reach 1ghz and to slowly step up the OC whilst launching N64 or PCSX which allows OC alterations without leaving the emulator. Apparently the NEON optimisations in recent PCSX versions mean it may be more unstable when OC'd and require lower settings but I'm still using r6 and it runs okay upto 1050mhz. Firefox may benefit from about 800mhz and using a 512mb swap file, which is easily made via Dave1234's SD card installer if you plan to boot from SD card, which has advantages space wise and a NAND setup to fall back on if it corrupts. Once you've found your max, do as Prometheus advises and set the limits for the slider in the GUI again to avoid overstepping it. Every unit varies.
Have fun
There's a clan of ninja's hereabouts B)
