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On 16/04/2024 10:59, Theo wrote:
> The Natural Philosopher 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 :-)
--- SoupGate-Win32 v1.05
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