Overclocking


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by UnaClocker » Sat May 19, 2012 8:42 pm
Being the UnaClocker, it's only fitting that I start the thread about overclocking in the Power Users section. :) I'd love to have a central thread like this where people can post their successes, and what settings they used to get them.
So far, I've been up to 900MHz on the core, probably need an overvolt to get beyond that. Keep in mind that overvolting voids your warranty (like that matters on a $35 computer!), but with the mods I have done and have in mind, it's the least of what would void my warranty. :)
I haven't messed with the GPU speed, nor the RAM speed yet. Anyone try those and see any kind of improvement?
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by JeremyF » Sat May 19, 2012 9:05 pm
Dom (a super smart guy with some affiliation with the Foundation) has been running on 1GHz for months.

http://elinux.org/RPi_config.txt#Overclocking_options -- Some info.
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by robwriter » Sun May 27, 2012 8:45 pm
Got my Pi up to:

900Mhz ARM
500Mhz RAM
275Mhz Video Core

with no overvolts, and its stable for a few hours. I find

Interestingly, if I go up to 950Mhz it doesn't boot at all, even if I increase the voltage. It works if I overvolt at 900, so unless I'm missing something it looks like I'm not going to hit 1Ghz :(.

Saw decent improvements in synthetic benchmarks with the ARM/RAM overclock.

Will try to max out the RAM and other settings this week - seems like you can get a little extra speed pretty easily.
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by normal » Sun May 27, 2012 10:20 pm
I just want to know what temps your getting beforeand after? I read somewhere that the RAM on the RPi is on the bottom of the Soc.. so would it be viable to try to cool the bottom of the board to get smoe extra MHz out of the RAM? Do you even need extra heatsinks/etc on the chip?
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by jamesh » Sun May 27, 2012 11:15 pm
normal wrote:I just want to know what temps your getting beforeand after? I read somewhere that the RAM on the RPi is on the bottom of the Soc.. so would it be viable to try to cool the bottom of the board to get smoe extra MHz out of the RAM? Do you even need extra heatsinks/etc on the chip?


Its actually on the top, but the effect is much the same. Even overclocked they don't get very hot, but you could try a tiny heatsink to see if it makes any difference to what speed you can get.

Overvolting void's the warranty BTW, whilst overclocking doesn't.
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by HAZZA24937 » Wed May 30, 2012 12:26 pm
Has anyone bothered with cooling attempts? Will it extend lifetime?
Also what exactly happens when the CPU is over volted, how exactly does it degrade it's lifetime?
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by Cavolo nero » Wed May 30, 2012 3:30 pm
Hi,

Just got my raspi working today, and ive already overclocked it to 900mhz cpu and sdram 500mhz. Ive noticed a marked improvement over the bog standard peformance!

Ive never overclocked a machine before - another educational benefit of the raspi! :D

I also found this site which was a good guide to a newbie like me.

http://www.senab.co.uk/2012/05/29/raspberry-pi-overclocking/
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by jamesh » Wed May 30, 2012 5:00 pm
HAZZA24937 wrote:Has anyone bothered with cooling attempts? Will it extend lifetime?
Also what exactly happens when the CPU is over volted, how exactly does it degrade it's lifetime?


I'm not sure why overvolting reduces lifetime, I'm sure Google can help there (it's the same for any semiconductor device).
Overvolting a Raspi will reduce the lifetime, but *probably* not enough to be relevant (e.g. from 20 to 10 years - made up figures but that sort of thing). BUT, since all these things are worked out statistically (no-one has ever run one for 20 years! You would be waiting even longer for your Pi!), we still need to void the warranty to be safe from lawsuits etc if someone does it and it only lasts 6months.
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by dom » Wed May 30, 2012 5:18 pm
These were my best setting:
over_voltage=6
arm_freq=1000
core_freq=500
sdram_freq=500

Running raspbian with those settings, and desktop/midori was pretty responsive.
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by reiuyi » Wed May 30, 2012 6:04 pm
It has been said a couple of times that increasing the voltage will decrease the lifespan of the SoC and probably also the RAM.

I'd like to know what sort of MTBF (mean time between failures) the BCM2835 is rated at. Is it rated for 10k hours, 50k hours, 100k hours, or perhaps 1M hours? What sort of decrease in lifespan are we looking at when the raspberry pi is over-volted beyond its factory preset?

My previous computer (AMD sempron 3000) was overclocked 25% and overvoltaged several deci-volts and after 6 years of intense usage it still worked fine. So whenever someone mentions the lifespan is decreased upon overclocking or over-volting, there needs to be some sources to back that statement up. Most chips are rated for like 100k hours of MTBF. Even if that was decreased by 50%, no user would ever encounter the average failure time.
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by AndrewS » Wed May 30, 2012 9:44 pm
When RPis are available in larger numbers I'll happily try over-volting my second one. But until then I don't want to risk voiding the warranty on the one precious Pi I do have ;)
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by zomzilla » Fri Jun 01, 2012 10:15 am
so, using Arch i set the frequency to 900 and rebooted just fine: but the cpu feels quite hot to the touch (outside of a mug of tea hot; almost feels like it would burn you but doesnt).

how can i
A) check temperatures
B)check the frequency of the CPU

thanks in advance
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by robwriter » Fri Jun 01, 2012 11:46 am
To see the speed run

cat /proc/cpuinfo

I can't remember what the number is called, but there's one that'll be close to the clock speed you set.

For temperature not sure there's an easy way - don't think the Pi has an inbuilt sensor, and I'd imagine measuring externall would be unreliable unless you have a fancy thermometer or want to attach a thermistor or thermocouple to the surface.
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by AndrewS » Fri Jun 01, 2012 12:20 pm
And of course any external thermometer would be measuring the temperature of the RAM, not the CPU...
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by markb » Fri Jun 01, 2012 3:53 pm
here are some temperature measurements:
after 10 mins of 100% CPU activity on standard Debian build

desk temp: 25.2 c
CPU/GPU: 48.6 C

created config.txt in \boot directory containing:

arm_freq=900
sdram=500
core_freq=275

10 minutes of browsing etc (seems quicker, but that is subjective)

desk temp: 24.9 C
CPU/GPU: 50.7C

I used a TN2 non contact infra-red thermometer, desk temp is an ambiant reading of the wooden desk Im using.
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by reiuyi » Fri Jun 01, 2012 6:40 pm
The device is rated for 50°C ambient temperature.

It's a mobile phone cpu. You cannot damage it with its own heat production!
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by zomzilla » Fri Jun 01, 2012 10:35 pm
Can you really not?

I was just paranoid that I had a hot Pi I guess.

Mind you, it looks like I have a good-un: 950 MHz is where I stopped (shows as 946.7 bogomips for some odd reason)
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by mahjongg » Fri Jun 01, 2012 10:50 pm
start with 701 MHz, and no overvolting, then clock it up slowly until it stops working at that speed, might be 800MHz, do not expect much more, then you can start trying overvolting it. The moment you do you you can wave goodbye to your guarantee, but who cares for a $35 (plus taxes and transport cost) device! start increasing slowly, and see if that helps. Measure the temperature of the POP SoC (they are thermally coupled so well, that it makes no difference that you are measuring the temperature of the RAM, as that will also be the temperature of the SoC), stop if the temperature reaches 50 degrees Celsius (that is 25 degrees more than room temperature). You could exceed that if you do not care about the longevity of the device, but I would not recommend going beyond 70 degrees or so.

Good luck, and may "the force" be with you.
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by dom » Fri Jun 01, 2012 11:09 pm
reiuyi wrote:I'd like to know what sort of MTBF (mean time between failures) the BCM2835 is rated at. Is it rated for 10k hours, 50k hours, 100k hours, or perhaps 1M hours? What sort of decrease in lifespan are we looking at when the raspberry pi is over-volted beyond its factory preset?


You never know for sure until that amount of time has passed.
We have models that estimate chip lifetime (with and without overvoltaging) but they are based on a large number of assumptions.

The models give big numbers though. The chips are predicted to run for tens of years. And overvoltage doesn't have *that* much predicted effect.

My guess? If you asked me to wager a tenner on whether a chip overvoltaged and overclocked to the max would still be working fine in two years time, I'd bet the tenner it would be.
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by robwriter » Sat Jun 02, 2012 9:19 am
My take is that it's going to last long enough for the Pi to be in plentiful supply. Having said that, I'm not running overvolted right now, as it doesn't affect the max clock speed that's stable.
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by mrbrades » Sat Jun 02, 2012 4:49 pm
Someone on the RasPi wiki got theirs up to 930MHz!

I have successfully set up config.txt to run using 930MHz arm_freq, 350MHz gpu_freq and 400Mhz sdram_freq.

I can't push it to 950Mhz though, it either hangs on 'waiting for /dev to be fully populated; or kernel panics.

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by Nburnes » Sat Jun 02, 2012 8:39 pm
mrbrades wrote:Someone on the RasPi wiki got theirs up to 930MHz!

I have successfully set up config.txt to run using 930MHz arm_freq, 350MHz gpu_freq and 400Mhz sdram_freq.

I can't push it to 950Mhz though, it either hangs on 'waiting for /dev to be fully populated; or kernel panics.

Matthew:out

My pi actually. Mine boots fully to to GUI at 950, but then things start getting wonky. I would overvolt, but definitely waiting until they are more easy to come by.
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by zomzilla » Sat Jun 02, 2012 10:38 pm
950 arm
350 GPU
500 ram

No over volt

Absolutely fine. change that to all defaults and 1000 arm however, and it won't even boot.

Is there any ways I can check sdram and GPU frequencies? I know I can look at the bogomips from cpuinfo, but is there similar for the other clocks?
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by dom » Sat Jun 02, 2012 11:06 pm
Something like lmbench should show an improvement with sdram freq and gpu_freq (specifically core_freq, as some of the clock cycles going to L2 cache and SDRAM are in the core_clock domain).
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by zomzilla » Sun Jun 03, 2012 9:06 am
Ok thanks Dom
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