Mundm28
Posts: 4
Joined: Sun Mar 06, 2016 9:45 am

Underclocking my pi3 to 900mhz

Mon Mar 07, 2016 8:44 am

Hi there,
I want to underclock my pi3 because it generates too much heat inside my gameboy case and as over/underclocking is not avaiable in raspi-config i do not know if i should undervolt it if underclocked to 900mhz.

Nine_Tails13
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Joined: Mon Mar 07, 2016 9:53 pm

Re: Underclocking my pi3 to 900mhz

Mon Mar 07, 2016 10:07 pm

Why not just use a Pi2B? Generates the same Hertz, has the same amount of ram I believe, functionally I've found little different, but I'm probably wrong on all accounts. And maybe you're running to intensive programs? Honestly I have no true idea, just spouting off what I know. ;) ;) ;)

Mundm28
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Re: Underclocking my pi3 to 900mhz

Tue Mar 08, 2016 8:24 am

Well i kinda liked wlan and bloetooth being integrated on the board for saving space in the case
and i was told the armv8 processor also works a bit more efficient at the same clockspeed than the armv7 of the pi2
so i thought for heating issues ill clock it down to the speed of the pi2 and keep the bonus of the newer cpu architecture plus wlan and bluetooth.

jahboater
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Re: Underclocking my pi3 to 900mhz

Tue Mar 08, 2016 9:15 am

Mundm28 wrote:Well i kinda liked wlan and bloetooth being integrated on the board for saving space in the case
and i was told the armv8 processor also works a bit more efficient at the same clockspeed than the armv7 of the pi2
so i thought for heating issues ill clock it down to the speed of the pi2 and keep the bonus of the newer cpu architecture plus wlan and bluetooth.
Just add this to /boot/config.txt and reboot.

Code: Select all

arm_freq=900
arm_freq_min=600

Mundm28
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Joined: Sun Mar 06, 2016 9:45 am

Re: Underclocking my pi3 to 900mhz

Tue Mar 08, 2016 3:35 pm

ok so i schould not write something with overvolt -1?
im asking because overvolt is common if overclocking to certain speeds and negative overvolt too i think?
or is it just that i would have to underclock it further before starting to undervolt it?

jahboater
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Re: Underclocking my pi3 to 900mhz

Tue Mar 08, 2016 3:46 pm

Mundm28 wrote:ok so i schould not write something with overvolt -1?
im asking because overvolt is common if overclocking to certain speeds and negative overvolt too i think?
or is it just that i would have to underclock it further before starting to undervolt it?
When I tried "over_voltage=-1" it failed to boot for some reason. You don't need to change the voltage.

Mundm28
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Re: Underclocking my pi3 to 900mhz

Tue Mar 08, 2016 3:48 pm

Thx dude :D

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DougieLawson
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Re: Underclocking my pi3 to 900mhz

Wed Mar 09, 2016 7:48 am

Nine_Tails13 wrote:Why not just use a Pi2B? Generates the same Hertz, has the same amount of ram I believe, functionally I've found little different, but I'm probably wrong on all accounts. And maybe you're running to intensive programs? Honestly I have no true idea, just spouting off what I know. ;) ;) ;)
This is the best suggestion in the thread.

The only difference between the 2B and the 3B is the 64-bit processor, for running a general purpose 32-bit workload they are identical.
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gkreidl
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Re: Underclocking my pi3 to 900mhz

Wed Mar 09, 2016 8:03 am

DougieLawson wrote:
Nine_Tails13 wrote:Why not just use a Pi2B? Generates the same Hertz, has the same amount of ram I believe, functionally I've found little different, but I'm probably wrong on all accounts. And maybe you're running to intensive programs? Honestly I have no true idea, just spouting off what I know. ;) ;) ;)
This is the best suggestion in the thread.

The only difference between the 2B and the 3B is the 64-bit processor, for running a general purpose 32-bit workload they are identical.
No, Dougie it's 2.3/1.9 = 1.211 times faster when running with the same clock speed (just the processor, ignoring the higher clock speeds used by the GPU parts).
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jahboater
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Re: Underclocking my pi3 to 900mhz

Wed Mar 09, 2016 8:19 am

Well i kinda liked wlan and bluetooth being integrated on the board for saving space in the case
and i was told the armv8 processor also works a bit more efficient at the same clockspeed than the armv7 of the pi2
so i thought for heating issues ill clock it down to the speed of the pi2 and keep the bonus of the newer cpu architecture plus wlan and bluetooth.
Yes, the 32-bit instruction set is almost identical, but there are underlying architectural improvements giving around 20-30% more speed - and the Wifi/BT. Sorry, but I agree with the OP.

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DougieLawson
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Re: Underclocking my pi3 to 900mhz

Wed Mar 09, 2016 11:16 am

Pick the right raspberry for the job. I downgraded a 2B to a B+ because the 2B wasn't anywhere close to maxed out. Using a 2B rather than a 3B when heat output is a critical part of the installation makes perfect sense to me. That 1.2 times speed increase may not be needed and it causes the 55°C to 80°C temperature increase.
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GTR2Fan
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Re: Underclocking my pi3 to 900mhz

Wed Mar 09, 2016 11:20 am

Agreed, Dougie. It's not compulsory to use the latest and greatest. Horses for courses.
Pi2B Mini-PC/Media Centre: ARM=1GHz (+3), Core=500MHz, v3d=500MHz, h264=333MHz, RAM=DDR2-1200 (+6/+4/+4+schmoo). Sandisk Ultra HC-I 32GB microSD card on '50=100' OCed slot (42MB/s read) running Raspbian/KODI16, Seagate 3.5" 1.5TB HDD mass storage.

gkreidl
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Re: Underclocking my pi3 to 900mhz

Wed Mar 09, 2016 2:20 pm

I do also agree. The Pi2 will keep its place. And my Pi3 will be the first one to get a heat sink.
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