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From: The Natural Philosopher <tnp@invalid.invalid>
Newsgroups: comp.sys.raspberry-pi
Subject: Re: What do I need to go with a Pi 4
Date: Tue, 16 Apr 2024 20:40:42 +0100
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On 16/04/2024 17:36, Pancho wrote:
> On 16/04/2024 10:59, Theo wrote:
>> The Natural Philosopher <tnp@invalid.invalid> wrote:
>>>> The Pi 4B will definitely throttle with only a ventilated case if it is
>>>> anything other than sitting idle all the time.
>>>>
>>> I am not interested in proof by assertion
>>> I had mine up to 130% on 'top' and it never made more than 76°C
>>
>> You do know that 'top' won't show throttling?  Throttling means the 
>> CPU is
>> clocked lower than the maximum frequency to reduce heat generation - top
>> will still show '100%' of CPU (for one core) but that will be 100% of a
>> lower clock speed.
>>
>> cat /sys/devices/system/cpu/cpu0/cpufreq/scaling_cur_freq
>>
>> shows you the current clock of CPU core 0 and:
>>
>> sudo vcgencmd get_throttled
>>
>> will tell you the throttling status:
>>
>>
>> #### get_throttled
>>
>> Returns the throttled state of the system. This is a bit pattern.
>>
>> | Bit | Meaning |
>> |:---:|---------|
>> | 0 | Under-voltage detected |
>> | 1 | Arm frequency capped |
>> | 2 | Currently throttled |
>> | 3 | Soft temperature limit active |
>> | 16 | Under-voltage has occurred |
>> | 17 | Arm frequency capped has occurred |
>> | 18 | Throttling has occurred |
>> | 19 | Soft temperature limit has occurred
>>
>>
>> For example if I run 'stress -c 4' then get_throttled gives me:
>> throttled=0xe0008
>>
>> so the temperature limit is in operation and throttling has occurred 
>> in the
>> past.  (this Pi4 has cooling, I can't remember but I think there's a
>> heatsink and fan in there)
>>
>> $ sudo vcgencmd measure_temp
>> temp=84.7'C
>>
>> so it's up near its thermal limit.
>>
>>>> I don't see the point of letting it throttling when an inexpensive fan
>>>> will keep it at full speed under any load.
>>>>
>>> I question that it will in fact throttle.
>>>
>>> Like so much 'everybody knows'  when you look at it it is in fact
>>> 'everyone believes because people selling fans told them so.
>>
>> 'Everybody knows' because they have evidence, not assertions.
>>
>>> The whole point of ARM is its lower power and lack of need for forced
>>> cooling
>>
>> Everyone's been thermally limited for maybe 15 years, it's just that Arm
>> cores have traditionally targeted a lower thermal envelope in devices 
>> where
>> forced air cooling isn't an option.  The way this works is that CPUs work
>> until they hit their thermal envelope and then throttle.  No popular
>> application processor for maybe a couple of decades has been able to 
>> power
>> all the silicon at once to max performance and stay within the thermal
>> budget.
>>
> 
> I think this thread is lacking precise, clear language, and people are 
> making false comparisons. Talking about ventilated cases is confusing, I 
> don't know what a thermal budget is.
> 
> There are four  points:
> 
> 1) Passive cases, where the case is a heat sink,  are enough to keep a 
> rPi4 below throttle temperatures, under any load, assuming ambient less 
> than 35C.
> 
> 2) With no heatsink at all the rPi4 will throttle under compute 
> intensive workloads.
> 
> 3) The rPi4 can perform useful day-to-day tasks without any heatsync, 
> passive or forced, without throttling. I ran Motioneye, cctv, on mine 
> for a couple of years before buying a case.
> 
> 4) Most of us don't use the rPi4 for continuous compute intensive tasks.
> 
> There, that should make everyone happy :-)
> 
> 

Mine runs hot because there is a TV hat bolted on top. And a SSD drive 
bolted underneath

that pushes up the case internals way more than the Pi does
But it is still happy and unthrottled

-- 
"Corbyn talks about equality, justice, opportunity, health care, peace, 
community, compassion, investment, security, housing...."
"What kind of person is not interested in those things?"

"Jeremy Corbyn?"