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How to properly overclock?

Posted: Sat Jul 14, 2012 9:09 pm
by payturr
Hey guys, my Pi is supposed to arrive sometime in the next 2 weeks, and I plan to overclock it, I just want to know exactly how to do it. I would like to know where I'd go to change the FSB frequency & how I should go about it - small increments like 20MHz increases every x amount of hours? And how high can I go without overvolting or causing the board to heat up? I plan to have it on 24/7 with no breaks (just gonna turn the peripherals off when I'm not using it) and I want it to be kept at a safe temperature. So how exactly do I overclock it and how high should I go thats healthy for my board? Thank you!
PS: This is the first computer I own that I'll be overclocking :geek:

Re: How to properly overclock?

Posted: Sun Jul 15, 2012 3:29 am
by Nburnes
http://elinux.org/RPi_config.txt#Overclocking_options

You simply make a text document named config.txt, place it in /boot with the settings you want and off you go. Most Pi's seem to easily do 800mhz, mine personally can get to 930mhz stable without any overvolting (which voids warranty btw). Then gpu freq is obviously the entire GPU overclocking, but my reading in the thread in this forum named "Overclocking" http://www.raspberrypi.org/phpBB3/viewt ... =29&t=6201 seems to cause instabilities, so like others I do simply a core freq increase.

Re: How to properly overclock?

Posted: Sun Jul 15, 2012 3:57 am
by payturr
Thanks man, I can just put it at 800MHz off the bat or should I start at like, 720MHz and work my way up?

Re: How to properly overclock?

Posted: Sun Jul 15, 2012 6:10 am
by jamesh
I'd start a 800. Pretty much guaranteed it can do that. Read the linked thread above- has everything you need.

Re: How to properly overclock?

Posted: Sun Jul 15, 2012 12:26 pm
by payturr
It wouldn't be too much? Cause I don't want the board to like, keel over just from a swift overclock to 800MHz

Re: How to properly overclock?

Posted: Sun Jul 15, 2012 12:50 pm
by sjfaustino
As long as you don't overvolt, AFAIK the most that will happen is the Pi will simply not boot or be unstable with errors and/or kernel panics.
In case that happens, just take the SD out of the Pi, insert into a computer, change the setting to something more conventional, save, pop the SD out of the computer and insert it back in to the Pi.

Happy testing :)

EDIT: forgot to mention, you really should do a burnin test after the overclock since the Pi just booting isn't a good test of stability. You should do an apt-get install cpuburn and use it to test for stability.

EDIT2: nevermind the cpuburn, it seems it doesn't work on the RPi. Just do:

sudo apt-get install bc
time echo "scale=2000; a(1)*4" | bc -l

Re: How to properly overclock?

Posted: Sun Jul 15, 2012 1:21 pm
by payturr
Well I can do that, but I don't know - just seems like too much to put on the Pi. Does everyone just jump to higher number clock speeds or?

Re: How to properly overclock?

Posted: Sun Jul 15, 2012 1:42 pm
by jamesh
Some people are getting 1Ghz without overvolt, so 800 is not going to be a problem. That's where I would start. If it doesn't start (But I think it will) you just need to drop it back in config.txt. No harm done. Only overvolting breaks the warranty.

Re: How to properly overclock?

Posted: Sun Jul 15, 2012 1:51 pm
by aaa801
Ive got mine upto 1200mhz with a 8 overclock
normaly you can get to 900 without a overclock

Re: How to properly overclock?

Posted: Sun Jul 15, 2012 2:28 pm
by payturr
Well I understand the whole overvolting issue, but I just wanna make sure that I could just jump from 700MHz to 800MHz with no issue, cause if it doesn't boot I rather just take my time and work my way up, cause I really HATE using Windows, in all honesty.

Re: How to properly overclock?

Posted: Sun Jul 15, 2012 4:51 pm
by jamesh
Dom is working on a patch to allow you to force a boot to standard settings using a jumper, so if you overclock it and it won't boot, you can still reboot to default, edit the config and recover the system. No windows involved. But I seriously doubt you will have any problems at 800Mhz.

Re: How to properly overclock?

Posted: Sun Jul 15, 2012 10:53 pm
by teh_orph
Why does the clock speed default to 700 MHz if we're expected to get such higher speeds at the same voltage? Do you know what percentage won't be able to go past > 750 MHz? (I'm thinking about yield etc)
Btw is the 700 MHz thing chosen by the foundation, or is that just what Broadcom guarantees?

Re: How to properly overclock?

Posted: Sun Jul 15, 2012 11:09 pm
by dom
teh_orph wrote:Why does the clock speed default to 700 MHz if we're expected to get such higher speeds at the same voltage? Do you know what percentage won't be able to go past > 750 MHz?
700MHz is guaranteed across all chips and across the temperature range. Almost all chips will run faster, especially at normal "room" temperature.

Re: How to properly overclock?

Posted: Mon Jul 16, 2012 3:28 am
by Lob0426
My RasPi seems to dislike anything over 800MHz. I have a theory that this is due to a below spec output from one of the voltage regulators. Probably one in the SoC. Vindicators likes to run at 900MHz with no overvolt. His starts wavering around 950. Is there a test point, that you can get to to test the voltage to the ARM Clock? It would be interesting to see what the different RasPii are turning out for voltage compared to the MHz. I seem to remember that there is more than one regulator in the SoC.

Re: How to properly overclock?

Posted: Mon Jul 16, 2012 5:29 am
by Flojer0
I just jumped by 100's until I hit instability and pulled back until I found it again. I got 950 without over-volt and 1200 with. Reading what others say it does appear VERY likely that you'll hit 800MHz without over-volt and 1GHz with over-volt very easily.

I do have some minor overclocking experience on my PC and have read quite a good deal on it. Even on a full desktop if you aren't pushing voltages up then all you have to do is watch for heat problems, and it has already been established by many in the know that heat isn't a problem with the pi. Allegedly even with over-volt it sounds like it is more the voltage than excess heat that will do it in.

Re: How to properly overclock?

Posted: Mon Jul 16, 2012 3:49 pm
by Lob0426
My 3v3 rail is at 3.28. My 1v8 Rail is at 1.8. So it is not the RG1(1v8) or RG2(3v3). I have been over the schematics and have not found a point to test for the voltage to the ARM processor Clock. It must be off of a regulator internal to the SoC. There are multiple 1v8 lines into the SoC but only one 1v8 regulator.

Re: How to properly overclock?

Posted: Tue Jul 17, 2012 12:07 am
by lucien_roach
aaa801 wrote:Ive got mine upto 1200mhz with a 8 overclock
normaly you can get to 900 without a overclock
What do you mean by an "8 overclock"?
I tried googling it but could find anywhere else that used this expression.

Re: How to properly overclock?

Posted: Tue Jul 17, 2012 1:57 am
by AndrewS
Lob0426 wrote:My 3v3 rail is at 3.28. My 1v8 Rail is at 1.8. So it is not the RG1(1v8) or RG2(3v3). I have been over the schematics and have not found a point to test for the voltage to the ARM processor Clock. It must be off of a regulator internal to the SoC. There are multiple 1v8 lines into the SoC but only one 1v8 regulator.
There are a whole bunch of VDD pins http://elinux.org/RPi_BCM2835_Pinout maybe you'll be able to probe some of them from underneath if you're careful / clever ?

Re: How to properly overclock?

Posted: Tue Jul 17, 2012 2:01 am
by AndrewS
lucien_roach wrote:
aaa801 wrote:Ive got mine upto 1200mhz with a 8 overclock
normaly you can get to 900 without a overclock
What do you mean by an "8 overclock"?
I tried googling it but could find anywhere else that used this expression.
I suspect he means an "8 overvolt" - http://elinux.org/RPi_config.txt#Overcl ... figuration

Re: How to properly overclock?

Posted: Tue Jul 17, 2012 2:15 am
by Vindicator
I have been using openarena as my stability test if I have it wrong the main menu will not appear but if it is right the main menu does appear in openarena.
Occasionally it will get into the main menu but will crash when going into the game itself.
In X I was able to run 950 cpu 500 ram and 350 gpu but in openarena 900 500 320 is what works.
I was able to get into X at 1000 but the keyboard would die out sometimes.

Re: How to properly overclock?

Posted: Tue Jul 17, 2012 1:17 pm
by lucien_roach
AndrewS wrote:
lucien_roach wrote:
aaa801 wrote:Ive got mine upto 1200mhz with a 8 overclock
normaly you can get to 900 without a overclock
What do you mean by an "8 overclock"?
I tried googling it but could find anywhere else that used this expression.
I suspect he means an "8 overvolt" - http://elinux.org/RPi_config.txt#Overcl ... figuration
I thought this too, I just wondered since I'm unfamiliar with the RPi hardware.

Re: How to properly overclock?

Posted: Tue Jul 17, 2012 9:04 pm
by aaa801
indeed i did :P

Re: How to properly overclock?

Posted: Mon Jul 30, 2012 2:11 am
by Snipez
I run my CPU at 930mhz seems the best.

Re: How to properly overclock?

Posted: Tue Jul 31, 2012 12:04 am
by FX4
Lob0426 wrote:My RasPi seems to dislike anything over 800MHz. I have a theory that this is due to a below spec output from one of the voltage regulators. Probably one in the SoC. Vindicators likes to run at 900MHz with no overvolt. His starts wavering around 950. Is there a test point, that you can get to to test the voltage to the ARM Clock? It would be interesting to see what the different RasPii are turning out for voltage compared to the MHz. I seem to remember that there is more than one regulator in the SoC.
More than likely your die just came from the edge of the wafer. Center die are faster and edge die are slower. This is caused by optical distortion in the photolithography process.

Re: How to properly overclock?

Posted: Fri Aug 03, 2012 12:42 pm
by jerrylamos
"properly" I've no technical familiarity with RasPi. I'm usually testing Ubuntu Alpha's and Beta's on netbook, notebook, tower. My interest in the RasPi is the lively forums.

What's running here is
sudo leafpad /boot/config.txt

arm_freq=900
core_freq=450
sdram_freq=450

shutdown, power off/on. Reboot wasn't happy.

This got wide margins on the display so

framebuffer_width=1366
framebuffer_height=768

overscan_top=-16
overscan_bottom=-16

save, shutdown, power off/on.

Running O.K. No overvolt, no heat sinks - will if I run across appropriate heat sink and adhesive here in the states.

Your milage may vary....

Jerry