Overclock?

I saw another newb where someone said they can overclock to 800mhz. What is the accepted/preferred way to overclock my Pi safely? I would like to start using it again but NetSurf kind of lags on it a bit… I’m thinking an overclock would help.

http://www.raspberrypi.org/forums/viewtopic.php?f=29&t=11214

Thanks Rick. I overclocked it to 800mhz. Seems a bit snappier. I’ve seen some of the other posts where they void the warranty bit. Is there a known good config for 900mhz? Not sure what I should set the SDRAM and GPU to.

AFAIK, the default overclock settings available for the Pi under the Linux distros are: [respectively ARM/Core/SDRAM/overvolt]

700/250/400/0 [default]
800/300/400/0
900/333/450/2
950/450/450/6
1000/500/500/6

Force_turbo must be set to =1 in all the above save the default (under linux overclocking is switchable on/off automatically, I believe; under RISC OS any overclock settings must apply full-time). You can also get various self-fit heatsinks from e.g. CJE Micros, which are probably a good idea if you are going for the more extreme overvolted options – they’re pretty cheap. FWIW I have heatsinks and have run mine regularly at 900/333/450/2 without apparent problems. But any overvoltage option is probably taking some risk with the hardware. OTOH, if you blow it up, it doesn’t cost much to replace….

OK.. last question is there a diagnostic or benchmark that I can run to verify?

There are two that I use; Michael Kubel’s !Firebench, from here: http://www.mikusite.de/pages/riscos.htm
and Richard Spencer’s RISCOSmark, which gives much more detailed information (e.g. as here: https://www.riscosopen.org/forum/forums/5/topics/466?page=9
) including graphics, memory, filing system and hard disk access speeds. I can’t see a website where you can get it: I’ll send you a copy of mine if you let me have an address.

if you blow it up, it doesn’t cost much to replace….

Unless you’ve also purchased Aemulor and an MPEG-2 license key which would up the cost to around £45.

I can’t see a website where you can get it:

No longer on line I think, however this might do you:

https://dl.dropbox.com/u/77062274/romark101.zip

A touch of the google and ye shall find.

@Mike: I take your point. I suppose every RISC OS Pi user has to balance the benefits of extra speed (which are palpable) with the risks entailed. I’m using a model B with separate power supply and am running it at 800/300/400 without over-volting, as I believe (without any concrete evidence either way) that allowing additional voltage may well shorten the Pi’s life, bearing in mind that under RISC OS this has to be a full-time option. OTOH, my Pi boots OK at 1000/500/500 with over-voltage set to 6, and goes like stink – but for how long? It would be very helpful to have some RISC OS-specific guidance from the RaspPi Foundation, but as this is unlikely, perhaps other RISC OS overclockers would care to respond to this thread with their experiences?

I always overclock at 900/333/450/2 – (RO 5.21).

“I always..”: since weeks? Months? (Dare I say) years?
Model?
Heatsink(s)?
Bespoke power supply, or USB?

Overclocking the CPU (only) to 800MHz should be fine.
I don’t use this configuration with RISC OS, but RaspBMC does it as a matter of course. It only ups the cpu_freq to 800MHz, the core (GPU) remains at 250MHz and the SDRAM at 400MHz.
As an observation, in August 2013, the GPU internal temperature with RaspBMC idle was between 48-52°C. When playing a 720p animé (H.264), it peaked to… actually… it stayed pretty much the same. Unlike my Atom which would jump 10-20°C when playing something. It doesn’t now, but that’s because I have the fan forced to 80% all the time. Noisy, but the SSD stays cool.

The official “voided warranty” logic used to be (force_turbo || current_limit_override || temp_limit>85) && over_voltage>0 but it looks like that may have changed to allow overvolting and higher frequencies – it seems from a casual read that the temperature is the important thing, not the voltage or speed, thus something (is this the OS or under GPU control?) will back off if the temperature gets up around 85°C. Means you may be able to get a Pi to run at double system bus speed, with the ARM up to a GHz. You may need heatsinks. Your RAM may object (especially if Hynix).
http://www.raspberrypi.org/introducing-turbo-mode-up-to-50-more-performance-for-free/

Re non warranty voiding overclocking. There may be a problem for RISC OS as there isn’t yet software that monitors the SoC temperature and reduces clock speeds when the =>85C ‘limit’ is reached.

From Ricks link:
“We are happy that the combination of only applying turbo when busy, and limiting turbo when the BCM2835’s internal temperature reaches 85°C, means there will be no measurable reduction in the lifetime of your Raspberry Pi.”

It’s only for a configuration with overvoltage.

“We’ve been doing a lot of work to understand the impact of voltage and temperature on lifetime, and are now able to offer a “turbo mode”, which dynamically enables overclock and overvolt under the control of a cpufreq driver, without affecting your warranty.”

It would be cool to have such a possibility in RISC OS, since even at 1 GHz (with a heat sink) you can push the Pi to the max for hours, without reaching 85°.

Without overvolt, 800 MHz is OK. 900 MHz sometimes OK. No more.

I always.. weeks? Months? (Dare I say) years?

You may. Since two years. Model B, no heatsink, powered through an Eminent 7-port USB hub using a 2-into-1 cable from CJE. The hub’s power cable has had an on/off switch inserted by a handy neighbour. I was fascinated to see him use a lady’s hairdryer to shrinkwrap the plastic insulation onto the wires. There are always new things to learn, especially if one has lived a life as sheltered as mine.

I’m happily running at 900mhz per GavinWraith’s post. I goofed up the RAM/Core setting and kept crashing (don’t try to over clock when you are tired!) going back over the post I fixed it. Works great.. thank you all! I had an unfortunate incident though, my SD card broke when my Pi fell off my desk. The Pi is fine, the SD card slot is fine.. but the card not so much. Had to order a new 8GB card.. time to re-do my RISC OS config!

Still on overclocking, I came across this site:
http://elinux.org/RPi_config.txt

where it has a potentially relevant reference to SD card stability, as follows:

++++++++++++
SD CARD USAGE WITH OVERCLOCKING
Stability of SD card operations when using overclocking is independent of:

• Filesystem type, ext4, NTFS or other.
• SD card vendor.
• The Raspberry Pi model.
• SD card size – verified for 16 GB and up.

What does matter is when you under-power your Raspberry Pi (that is, less than the Raspberry Pi base setup specifications!).
There initially was an increased likelihood of SD card corruption when using overclocking. This is no longer an issue (with firmware from Nov 11 2013 or later).
+++++++++++

I don’t know how relevant this is to RISC OS use, but I thought it worth bringing up in case anyone can comment from a more knowledgeable viewpoint than mine.

I’ve got my B+ model running at 1000mhz cpu and 500mhz gpu and memory with a over-voltage of 4. I’ve fitted heatsinks to the main 2 chips. Got supplied a 3rd heatsink but the voltage regulator is too small on the B+ to use it. I will be adding a fan shortly once I’ve received my case.

My last risc os computer was a 233mhz strongarm risc pc and the pi seems an absolute world apart in performance. Very impressed with this little computer. Shame about no decent browser though.

Can you improve overclocking on risc os by setting 3d, camera and mpeg decoding clocks low which aren’t used by Risc OS? Can you set them to 0 or does it have to be an actual low value?

Can you improve overclocking on risc os by setting 3d, camera and mpeg decoding clocks low which aren’t used by Risc OS? Can you set them to 0 or does it have to be an actual low value?

From the Pi’s configuration FAQ: The GPU core, h264, v3d, and ISP blocks all share a PLL and therefore need to have related frequencies. The CPU, SDRAM and GPU each have their own PLLs and can have unrelated frequencies.

How related do they need to be, what is the absolute minimum h264, v3d and isp can be set while the gpu core is at 500mhz lets say. Is 0 a possibility if the feature is completely un-needed?

Hi Martin. For those sort of questions the raspberrypi.org forums are a better place to ask. They are frequented by Broadcom and ex Broadcom engineers who are the only people really in the know at that level.

If Martin gets an answer, can he please report it back here?

I’m supposing the information would also be useful for boosting the performance of normally-clocked Risc OS on both RaPi & Panda.

@Chris: “Up to a point, Lord Copper..”. I have searched these forums, and there are indeed highly expert people there, and lots of information; the problem is, all their advice is in a Linux context, and as we know, the Pi’s Linux distro allows for (a) dynamic overclocking; and (b) temperature-sensitive downclocking (i.e., if the Pi’s CPU exceeds 85 deg.C, the default clock rates are restored). RISC OS allows for neither of these things: an overclocked RO Pi is permanently in that state regardless of temperature etc. What if I set my 1GHz Pi to run for 40 hours continuously while it clones a 32GB SD Card; is that more or less overload than might be encountered under Linux? I have no idea, and I doubt if the Linux boys know either. So I think the experiences of RISC OS Pi users with overclocking is still relevant.

Dynamic overclocking would be cool under RISC OS.