Yesterday we released our first Raspberry Pi OS image built on top of Debian Bullseye. Alongside the usual package upgrades that accompany every major Debian release, this provides a more modern composited desktop environment on Raspberry Pi 4 boards with 2GB or more of memory, and retires our legacy display and camera support in favour of KMS and libcamera respectively.
1.5GHz to 1.8GHz
But some of you may have noticed another upgrade. Users with recent Raspberry Pi 4 devices will find that their default turbo-mode clock has increased from 1.5GHz to the 1.8GHz used on Raspberry Pi 400. “Recent” in this case means any 8GB Raspberry Pi 4, or a 2GB or 4GB board with the extra components circled in the image below. This is the dedicated switch-mode power supply (“switcher”) for the SoC core voltage rail, and was introduced when we shuffled the allocation of switchers to rails to support 8GB.
Through extensive testing on the production line, we have qualified an operating voltage for 1.8GHz, and satisfied ourselves that the new switcher is able to supply enough current to run even the heaviest workloads at that speed.
Overclocking older Raspberry Pi devices
What about older devices? Even the launch-variant Raspberry Pi 4 has gained a reputation for overclockability, and most units will run most workloads at well over 1.5GHz with a little extra core voltage. The latest firmware (included in the Bullseye image) will even do its best to figure out the best voltage to apply for a given overclock. To manually replicate the new operating point on an older board, just add the following line to your config.txt file:
If you encounter stability issues, you can try backing off the frequency in 50MHz steps, or manually setting an overvoltage. But remember: playing with clocks and voltages can render your SD card (temporarily) unbootable, so make sure you have another card (or another computer) on hand that you can boot with to restore your config.txt to good sense.