Overclocking a Raspberry Pi 1, model B?

1st Official Post

    Hi there,

    I got LibreELEC on a RPi1, and, while it's functional, using the extensions or simply navigating folders is painfully slow. It's not unusual for a simple Youtube request to take one or two full minutes. Now, I get it, running a 2017 OS on 2012 hardware is bound to be slow. But switching to a RPi 3 is not an option at the moment due to the high price tag ($50+).

    As I understand, LibreELEC was first meant to be stable, and thus does not allow for easy overclocking.

    But the slowness…

    I attempted to modify the /flash/config.txt following these instructions (meant for OpenELEC, but both systems are quite similar in this regard), trying the "medium" settings, plus some overvoltage so as to allow for more stable operation.

    Code
    force_turbo=0####################### Overclock mode settings.## default recommended values are: arm_freq | core_freq | sdram_freq | over_voltage# no overclocking : 700 | 250 | 400 | 0# mode 'Modest' : 800 | 300 | 400 | 0# mode 'Medium' : 900 | 333 | 450 | 2# mode 'High' : 950 | 450 | 450 | 6# mode 'Turbo' : 1000 | 500 | 600 | 6# mode 'Pi2' : 1000 | 500 | 500 | 2
arm_freq=900core_freq=333sdram_freq=450over_voltage=2over_voltage_sdram=4

    But it doesn't hold after reboot. Although LibreELEC does boot, it appears unable to latch on the network and keep its DHCP-assigned IP (Ethernet, not WiFi). CPU temperature is normal, around 57C with no heatsink under medium load (never goes below 25%), just naturally vented open-top case. Seldom freezes or crashes.

    It is currently running off a slightly modified power supply previously used for an old external hard drive. It has both 12V and 5V rail, able to push 2A on both. The 12V rail had no load, and when the RPi is running, a USB voltage/ current monitor records about 180mA drain on the 5V rail, but only 4.64V. When I load the 12V rail with a small 12V LED bulb (around 190mA drain), the 5V climbs to 4.77V, and I can reach 4.85V if I plug a DVD drive (idle). Thus, the 5V real voltage seems dependent of the 12V load.

    Is the 5V rail voltage too low to ensure stable operation with overclocking?

    What is the maximum real voltage an RPi 1 can take without damage? 5.1V. 5.2V?

    Is my /flash/config.txt missing parameters to ensure stable overclocking?

    Is the CPU simply too hot at 57C?

    Or some other reason why it fails?

    • Official Post

    You will need a PSU that delivers 2.5-3 amps and a heatsink to have reasonably stable overclocking on any pi board. If you're using MPEG2 encoded media you'll also want the codec license so things are hardware decoded.

    • Official Post

    Pi hardware is happy to run quite hot, but if you want to overclock *and* be stable you need it to run at the lowest temperature possible. That just means using a case with a heatsink (like the Kodi flirc case) or a stick on heatsink.

    There are two likely issues apart from the supply. First is the cable from the supply. Shorter and thicker is better. It doesn't matter how good the power supply is if the cable drops too much voltage, and you'll struggle to measure voltage spikes without decent test gear. Second, overclocking is never guaranteed Chips are manufactured to a specification covering a range of speed, power supply voltage, temperature etc. Where there are multiple chips (RAM, peripherals, etc) each has its own range of parameters within which it will work. Sometimes these will only overlap quite near the nominal operating conditions. Overclocking requires all parts to be able to work equally well outside of these intended specifications. Sometimes it is easy. Sometimes it's almost impossible. Sadly, the culture around devices like the Pi encourages users to try things like overclocking to the point where it is expected that it will always work. Sometimes it won't. And if it does, the speed increase may not result in a proportionate time saving if other elements (like USB / SD storage) still take just as long.

    (And for the mods... Why does the forum software treat the word "s-c-i-e-n-c-e" as censored and not permissible in posts?)

    Quote from chewitt

    Pi hardware is happy to run quite hot, but if you want to overclock *and* be stable you need it to run at the lowest temperature possible. That just means using a case with a heatsink (like the Kodi flirc case) or a stick on heatsink.

    Definitely true for an RPi3, but just about everything I read at the time for an RPi1 was along the lines of 'Don't waste your time.'

    eg from popcornmix back in the mists of 2013:

    'No need for heatsinks. We believe 85C is the safe temperature limit (and overclock will disable if that is hit).

    However I've never heard of anyone who's hit that (and I've deliberately tried).'

    On the basis of that (and many similar posts) I've never bothered with a heatsink with my Pi1s.

    A Pi (even an RPi3) will never need more than a 2A supply unless you're running (probably multiple) hard drives from it - my Pi3 (not overclocked) has been happy for the past 12 months on a 1A supply. What matters is consistent voltage - which is a lottery unless you're using a known supply.

    On RPi1 (non-plus model) you also may need to short out the polyfuse F3 - it can contribute to a significant voltage drop.

    Even a very short dip on the voltage rail might make your RPi crash, so if in doubt stick to the official RPi power supplies - they are known to work well.

    Back in the day I had very good success (more than half a dozen installs for friends & family) with official RPi power supply and the following overclock:

    Code
    arm_freq=1000
core_freq=500
sdram_freq=500
over_voltage=6

    so long,

    Hias

    I tested the overclcok with two different power supplies, a generic USB charger rated at 1A, and a Samsung USB charger rated at 2A. I plugged a USB voltage / intensity monitor and measured without load, and with the Pi. The generic showed a large voltage dip when under load, but the Samsung charger increased from about 5.01V to 5.23V@800mA. How is this charger property called?

    I still don't get why the measured current so much greater when the Pi runs off 5.23V than from 4.65V.

    Since then, I overclocked to 950MHz, no issues except a high pitched hiss coming from the TV speakers that changes when I select a different movie. Don't know how to solve it.

    Playing a large movie stored on the SD card, CPU temperature shoots to 68º, the RPi B sitting in an enclosure with no special cooling enhancement.