Raspberry Pi System Frequency

Yesterday I read in an article that Raspberry Pi operates at 700MHz but it can be overclocked to 1GHz. Following some tutorials on the Internet, I also read that System Timer increases every microsecond. These two sentences confused me.

Which of them is true? How can the RPi be overclocked in RISC OS?

To overlcock, you need to alter the CPU clock in config.txt read the section on Overlocking Options.

Under RISCOS, config.txt is in !Boot.Loader

There’s more than one clock, so overclocking doesn’t make the wall clock spin faster.
(I once did a patch for IOMD machines that made all the timers spin about 30x faster – pointless, but was fun to watch the seconds rush past)

Hi Adrian, as Jon says above, you need to open !Boot.Loader.config.txt and change the arm_freq, core_freq and cpu_freq values. Approved combinations are, in the above sequence:
700/250/400/[default]
800/300/400 and add the line at the bottom: force_turbo=1
900/333/450 and add the lines at the bottom: over_voltage=2 and: force_turbo=1

Both of the above upclock options should be stable and the Pi seems to tolerate them for extended periods* – but no guarantees! If you’re feeling braver or have a serious need for speed, you can go to

950/450/450, over_voltage=6, force_turbo=1
1000/500/500, over_voltage=6, force_turbo=1

[*900/333/450 for 2 years in the case of one user; over 4 months so far here]