"Overvolt" and power supplies

[swizzard]

I'm not sure if this is an appropriate question for the 'newbie' section, but it seems too obvious/simple for the 'power users' section, so:

The overclocking options available via raspi-config refer to, e.g., 'overvolt 2.' I understand that this means increasing the voltage going through the pi, but am confused about how that interacts with power supplies. If I set my pi to the "Medium" overclock setting (2 overvolt), but am powering it with a regular 5V power supply, will that
a) not actually improve the performance of my pi at all or
b) cause it not to run for lack of power?

If it's the case that one needs to supply exactly X volts of power to the pi, where X = 5 + overvolt value, can anyone recommend a place to get, e.g., a 7V (or 11V) power adapter (ETA: in the US)? Most that I've seen are 5, 9, or 12V.

[Cloudcentric]

http://elinux.org/RPi_config.txt#Overclocking_options

[swizzard]

over_voltage ARM/GPU core voltage adjust. [-16,8] equates to [0.8V,1.4V] with 0.025V steps. force_turbo will allow values higher than 6. Default 0 (1.2V)

OK...forgive me being dense, but does that mean 'overvolt 6' means the Pi will need 5 + (6*0.025) = 5.15V to run? Is that within the realm of a "regular" 5V adapter (say, an iPhone adapter or powered USB hub)? Will Something Bad happen to my Pi if I can't supply it 5.15V?

[mad-hatter]

Hello,

The over voltage setting is internal to the Pi.
The Pi still needs a 5V supply.
There is a limit on the over volt setting, exceed it and your warranty will be void.

Regards

[Wheel_nut]

No. In the context of Overclocking, overvolting refers to raising the ON-CHIP generated voltage driving the System-on Chip Processor.

The 5V input to the RPi is stabilised at 3.3V on the Board and this lower voltage drives everything on the SoC. Other voltages may be derived on the SoC and the Processor voltage is one such voltage.

Before someone jumps on me, I should add that the LAN subsystem is powered directly off the 5V input voltage and the LAN subsystem also derives its internal voltages within the subsystem.

[pluggy]

The processor itself runs at an even lower voltage (1.8v I think) . The voltage of the power supply won't matter, but the current may. But what the processor uses on most Pis (aka the Model B) is pretty low, since the LAN chip takes the lions share of the juice the Pi itself uses. Unless your power supply is on the edge of working, overclocking probably won't push it over.

[fishxz]

thats a good question. cause all of my 5 sd get corrupted + freezes if i set overvoltage to 1 or above. is this a openelec related problem? i have class 10 samsung sd and a power supply with 5v and 1200ma.

[malakai]

Could be related to your card or the Pi itself overclocking of any setting seem to vary from Pi to Pi some can handle the most extreme settings some can't tolerate it.

[FTrevorGowen]

fishsx: Are you using raspi-config to set your over-clocking/over-voltage options? As I understand matters, whilst editing the config file directly may be OK, raspi-config is more likely to create "stable" combinations. Re: your 5V 1200mA PSU - does it appear as a "verified device" in the wiki. The 1200mA spec. may be misleading (or rather be the short-circuit current, rather than the maximum associated with a minimum voltage suitable for the Pi - around 4.5V). I've come across "5V 1000mA" PSU's that can only deliver 500mA of "useful current"*. Trev.
* see my webpages for more info.

[fishxz]

its a "HNP06" power adapter and its listed as supported. i set my clock direct in config.txt cause i think there is no raspi-config for it? never heared about this before. its rly annoying to cant use over voltage

[FTrevorGowen]

fishxz: IIRC "raspi-config" first appeared in Wheezy Raspbian in the autumn of 2012**. It normally runs automatically when you first boot from a clean, fresh image on the SD card, providing options to change user pi's password, setup key board options, timezone, expand the filesystem to fill the SD card, overclocking & memory options etc. etc. However you can re-run it later from your (pi) login prompt thus: sudo raspi-config
If "raspi-config" isn't found (its full location is /usr/bin/raspi-config) either you're not using Wheezy Raspbian or you have a (very) old version of it.
For example my login banner etc. shows this:
"Linux raspiblue 3.2.27+ #250 PREEMPT Thu Oct 18 19:03:02 BST 2012 armv6l

The programs included with the Debian GNU/Linux system are free software;
the exact distribution terms for each program are described in the
individual files in /usr/share/doc/*/copyright.

Debian GNU/Linux comes with ABSOLUTELY NO WARRANTY, to the extent
permitted by applicable law.
Last login: Tue Mar 5 12:17:30 2013 from (IP address removed)
pi@raspiblue ~ $ which raspi-config
/usr/bin/raspi-config"

NB: Because I have several Pi's they've been "renamed" via edits of /etc/hostname & /etc/hosts
Trev.

**I've just checked the wiki - it "first appeared" in the June release, the over-clocking (as opposed to over-scan) option was probably added in the autumn after B2 Pi's became available. T.