Fan Speed Control
Posted: 10 Dec 2023, 20:29
While using the TOS6 Beta I had a disconcerting incident where the HDD Overheat alarm went off (65C). When I investigated it appeared that the (single) fan had stopped (?question failed?). Upon further investigation it looked like there was an issue with the fan speed control. Now back to the future .....
Stripped down system and connected fan to 'cpu fan' socket. (I bought the box 2nd hand and I don't care!) As might be expected, the fan ran continuously without issue. (Not a long test but sufficient, imo). So I did a complete re-install of virgin TOS 5.1.95.
What I found was interesting and not what I expected.
Using the variable speed fan setting, the fan would do as expected and run at varying speed (including zero rpm).
However, using any of the fixed speed settings, the fan will run in bursts at the given speed, but would also stop (zero rpm) for periods of time. This is not what I expected. In the absence of a clear algorithm for the control, I suspect (because the control panel is hard to refresh) that there is a factor based on CPU temp of 36C. When temp drops to that level, the fan seems to stop.
If for any reason, the cpu temp remains low the fan may not react to increasing HDD temp as I experienced. (I believe that in previous versions, the HDD temp was highly weighted to be the controlling factor, but that this was changed.) In this particular unit (F2-221) I am running HGST 7200rpm drives and they run hotter than most. This can be detrimental.
It may also be a situation where there is insufficient voltage to re-start the specific fan installed (oem in this case) but that needs much deeper investigation than I can perform.
If I set a 'fixed' speed for the fan, I do expect the fan to run continuously and not stop for some arbitrary reason.
Stripped down system and connected fan to 'cpu fan' socket. (I bought the box 2nd hand and I don't care!) As might be expected, the fan ran continuously without issue. (Not a long test but sufficient, imo). So I did a complete re-install of virgin TOS 5.1.95.
What I found was interesting and not what I expected.
Using the variable speed fan setting, the fan would do as expected and run at varying speed (including zero rpm).
However, using any of the fixed speed settings, the fan will run in bursts at the given speed, but would also stop (zero rpm) for periods of time. This is not what I expected. In the absence of a clear algorithm for the control, I suspect (because the control panel is hard to refresh) that there is a factor based on CPU temp of 36C. When temp drops to that level, the fan seems to stop.
If for any reason, the cpu temp remains low the fan may not react to increasing HDD temp as I experienced. (I believe that in previous versions, the HDD temp was highly weighted to be the controlling factor, but that this was changed.) In this particular unit (F2-221) I am running HGST 7200rpm drives and they run hotter than most. This can be detrimental.
It may also be a situation where there is insufficient voltage to re-start the specific fan installed (oem in this case) but that needs much deeper investigation than I can perform.
If I set a 'fixed' speed for the fan, I do expect the fan to run continuously and not stop for some arbitrary reason.