sousadev
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Joined: Wed Nov 18, 2020 4:50 pm

Limit RPi 5 computational power to use it has it was an older RPi

Tue Nov 28, 2023 10:15 am

Hi, I am using my RPi 5 - 8gb for my research work for my master thesis and I would like to know if there is a (easy) way to limit my latest RPi computational power so it runs similarly to older models. I would need this to check if my work would run on older devices without having to test directly on them.

I know that it will never be the same has testing on the actual models, but I won't be having access to all RPi models so that's the best I could do.
Has anyone ever done anything similar to this? If yes, how did you?

Thank you.

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kerry_s
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Re: Limit RPi 5 computational power to use it has it was an older RPi

Tue Nov 28, 2023 10:35 am

you can try underclocking
arm_freq=1000

not sure about ram/memory though, i recall there was a setting, not sure if it would work and can't recall the syntax.

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Milliways
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Re: Limit RPi 5 computational power to use it has it was an older RPi

Tue Nov 28, 2023 10:51 am

sousadev wrote:
Tue Nov 28, 2023 10:15 am
Hi, I am using my RPi 5 - 8gb for my research work for my master thesis and I would like to know if there is a (easy) way to limit my latest RPi computational power so it runs similarly to older models. I would need this to check if my work would run on older devices without having to test directly on them.

I know that it will never be the same has testing on the actual models, but I won't be having access to all RPi models so that's the best I could do.
Has anyone ever done anything similar to this? If yes, how did you?

Thank you.
I can't get my hands on a Pi5. I would quite happily swap your Pi5 for a Pi4.

jamesh
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Re: Limit RPi 5 computational power to use it has it was an older RPi

Tue Nov 28, 2023 11:17 am

Add "total_mem=1024" or similar to /boot/config.txt to reduce memory. I think that works on Pi 5.
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kerry_s
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Re: Limit RPi 5 computational power to use it has it was an older RPi

Tue Nov 28, 2023 11:32 am

jamesh wrote:
Tue Nov 28, 2023 11:17 am
Add "total_mem=1024" or similar to /boot/config.txt to reduce memory. I think that works on Pi 5.
yeah, that's the 1, haven't seen in along time. :lol:

sousadev
Posts: 4
Joined: Wed Nov 18, 2020 4:50 pm

Re: Limit RPi 5 computational power to use it has it was an older RPi

Tue Nov 28, 2023 11:55 am

Thank you all! I will see what I can do by changing these parameter on the config file.

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rpdom
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Re: Limit RPi 5 computational power to use it has it was an older RPi

Tue Nov 28, 2023 12:08 pm

I don't know if the maxcpus=n option still works in config.txt. If you set it to 1 or 2 and limited the speed to 1500, that would be more like a Pi 2 or 3.
Unreadable squiggle

sousadev
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Re: Limit RPi 5 computational power to use it has it was an older RPi

Tue Nov 28, 2023 12:51 pm

rpdom wrote:
Tue Nov 28, 2023 12:08 pm
I don't know if the maxcpus=n option still works in config.txt. If you set it to 1 or 2 and limited the speed to 1500, that would be more like a Pi 2 or 3.
It didn't work on configs.txt, but it does work on /boot/cmdline.txt. Just adding maxcpus=1 (or wtv you want) at the end of the line

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bensimmo
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Re: Limit RPi 5 computational power to use it has it was an older RPi

Tue Nov 28, 2023 1:37 pm

What's the minimum speed the 5 will run at, iirc it set to 1GHz by default for it's sleepy/idle state.
Will it go lower, like 400 or 600MHz.

It would be easier to show a slightly fast PiZero then,

I would target PiZero2 (512MB), Pi4 (1GB, 2GB) and Pi5 4GB

The Pi3 is probably pushed out by the Pi4 as the old Pi now, and the Zero2 is the slowest of the "3 series" Pi.
You could clock the RAM down to maybe and stick the SD card down at a slower speed, I'm sure there was an option somewhere in that big README in the overlays, stick it back down at 50DDR and 50 SDR, restrict that data transfer speed.?

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