OK I got this.
"run away".
First you have to state the conditions for thermal testing.
ie.
Thermal runaway is where the temperature of the CPU builds up and hits a limit because the cooling abilities of the heatsinking are exceeded by the build up of heat from the CPU.
This is related to the AMBIENT temperature of the surrounding air and the ability to sink the temperature differential.
In summer here we have typically ambient temperatures of 35-40C.
ie . No aircon here.
The current ambient temperature in this room is 16-17C. (winter)
this is what I get NOW.
vcgencmd measure_temp temp=33.6'C-temp-35.0'C.
This means with the CPU moderately loaded but running X-windows,
there is a differential of 17-18C with the very latest iteration of heatsinking and fan running.
Without the fan running, the CPU temp soars to 59C* at idle with no X, so a temp differential of 28-30C.
I spent a year getting this sorted.
free -m records
total used free shared buff/cache available
Mem: 3806 1314 1469 63 1022 2353
Swap: 511 330 181
top - 13:49:22 up 2 days, 17:42, 1 user, load average: 0.93, 0.58, 0.51
Tasks: 219 total, 2 running, 217 sleeping
--
Now, if we change ambient temp to 40C, without the fan, it is clear the CPU with a temp differential of 28-30C will throttle (70C) leading to an inability to keep pace with tasks.
This is the textbook definition of thermal runaway.
I discussed this only yesterday with Oratek, who were astonished I manage to keep idle temps down to 29C. (with a 12V fan running at 5V).
So, the difference between idle, and doing moderate but useful tasks is roughly 6-7C.
If instead we start to run HD video with HD sound the CPU temp jumps to around 37-42C in winter temps.
If we increase ambient temp by 20C this means we are going to run the CPU somewhere in the 60-65C region.
This is kinda limit "doable" so we need to increase airflow in those conditions.
Just not to make too fine a point on this.
Previous iterations of the case and cooling, (attempting to run HD video in summer) would result in the entire system keeling over within no more than 10 minutes of HD video.
Being as the general idea is to install the CM4 system inside a case already running at 43-48C I think you begin to understand the meaning of "unuseable" and thermal non-viability.
As we are all now very well aware of the you can't get a "something for nothing" situation, it strikes me the release of RPI5 in the winter period would not have allowed testing in the conditions I described in detail above.
conclusions:-
1/ In fact I could maintain with absolute certainty a RPI5 will literally fall over and die if subjected to the same sort of testing in summer conditions running a HDMI projector to a large screen outdoors on summer evenings.
2/ I have to add I suppose this is my main router board-has a SIM card installed, a M.2 Modem attached to the port behind, and at the same time has a hi end DAC with VLC running CLi with a web interface.
HDMI output can be to a projector or a large screen Sony TV with sound over balanced XLR to 2 large amplifiers for home cinema.
It also is running home assistant and Asterisk with MariadB & Docker + DSP at the same time.
So the idea is for it to run as a dedicated SIP server/SIP forwarder.
'nuff said?![:)]( "Smile")
"run away".
First you have to state the conditions for thermal testing.
ie.
Thermal runaway is where the temperature of the CPU builds up and hits a limit because the cooling abilities of the heatsinking are exceeded by the build up of heat from the CPU.
This is related to the AMBIENT temperature of the surrounding air and the ability to sink the temperature differential.
In summer here we have typically ambient temperatures of 35-40C.
ie . No aircon here.
The current ambient temperature in this room is 16-17C. (winter)
this is what I get NOW.
vcgencmd measure_temp temp=33.6'C-temp-35.0'C.
This means with the CPU moderately loaded but running X-windows,
there is a differential of 17-18C with the very latest iteration of heatsinking and fan running.
Without the fan running, the CPU temp soars to 59C* at idle with no X, so a temp differential of 28-30C.
I spent a year getting this sorted.
free -m records
total used free shared buff/cache available
Mem: 3806 1314 1469 63 1022 2353
Swap: 511 330 181
top - 13:49:22 up 2 days, 17:42, 1 user, load average: 0.93, 0.58, 0.51
Tasks: 219 total, 2 running, 217 sleeping
--
Now, if we change ambient temp to 40C, without the fan, it is clear the CPU with a temp differential of 28-30C will throttle (70C) leading to an inability to keep pace with tasks.
This is the textbook definition of thermal runaway.
I discussed this only yesterday with Oratek, who were astonished I manage to keep idle temps down to 29C. (with a 12V fan running at 5V).
So, the difference between idle, and doing moderate but useful tasks is roughly 6-7C.
If instead we start to run HD video with HD sound the CPU temp jumps to around 37-42C in winter temps.
If we increase ambient temp by 20C this means we are going to run the CPU somewhere in the 60-65C region.
This is kinda limit "doable" so we need to increase airflow in those conditions.
Just not to make too fine a point on this.
Previous iterations of the case and cooling, (attempting to run HD video in summer) would result in the entire system keeling over within no more than 10 minutes of HD video.
Being as the general idea is to install the CM4 system inside a case already running at 43-48C I think you begin to understand the meaning of "unuseable" and thermal non-viability.
As we are all now very well aware of the you can't get a "something for nothing" situation, it strikes me the release of RPI5 in the winter period would not have allowed testing in the conditions I described in detail above.
conclusions:-
1/ In fact I could maintain with absolute certainty a RPI5 will literally fall over and die if subjected to the same sort of testing in summer conditions running a HDMI projector to a large screen outdoors on summer evenings.
2/ I have to add I suppose this is my main router board-has a SIM card installed, a M.2 Modem attached to the port behind, and at the same time has a hi end DAC with VLC running CLi with a web interface.
HDMI output can be to a projector or a large screen Sony TV with sound over balanced XLR to 2 large amplifiers for home cinema.
It also is running home assistant and Asterisk with MariadB & Docker + DSP at the same time.
So the idea is for it to run as a dedicated SIP server/SIP forwarder.
'nuff said?
Statistics: Posted by easterly_gales — Fri Feb 09, 2024 1:26 pm