The DH55TC board utilizes Intel's Quiet System Technology (QST) for its environmental monitoring and fan speed control; it does not utilize the capabilities of the SIO. Your should ignore the SIO's sensor readings; while some sensors will provide valid readings, most do not.
I suggest that you use a tool - Intel Desktop Utilities (IDU) (free), AIDA64 (free to try) or SpeedFan (free) - that properly provide support for QST.
This is *still* displaying SIO sensors. You may have to manually configure it to remove (disable) the SIO sensors and get the correct ones displaying. At least for a short while, while we resolve this issue, install Intel Desktop Utilities so that we can see (only) the appropriate sensors. You can fiddle with these other applications later. Here is a link to download this package from Intel's Download Center: https://downloadcenter.intel.com/download/20488/Intel-Desktop-Utilities Download Intel® Desktop Utilities. Let's resolve whether you have an issue related to temperatures.
Well, I would conclude a few things from this,
Do you not have chassis cooling fans?
OK, just to be sure, shutdown the system and unplug it from the wall. Wait 15 minutes and then plug it back in and power it up. Once in Windows, let the system sit idle for 15 minutes and then used IDU to get a new set of readings.
Ok, two things...
Are your fans connected to the board's fan headers? If not, you can ignore this paragraph. If they are, however, you need to do a fan redetection. Go into BIOS Setup, navigate to Advanced and then into the scene for monitoring and fan speed control. There should be an option to select that a fan redetection take place on the next reboot (sorry I cannot be more specific, it's been a lot of years since I last looked at this - and don't have a board with which to do so). Exit from BIOS Setup with a save. The fan redetection should take place during the reboot. After booting into Windows, start up IDU's GUI and then click on Options, Set Sensor Threshold and then Fans Redetect. This redetect will take place during the next Windows restart...
If your system was idle when you took this snapshot of these readings, there is definitely a concern with airflow over the motherboard. It is possible that this is caused by normal degradation over time but I doubt it. I have also seen situations where big graphics cards impede airflow but you did say you have a fan blowing in from the side. It is also possible, if your fans are plugged into the board's fan headers, that the lack of detection is causing the fans to not be accelerated when needed (doing the redetection may help with this. Finally, I have also seen situations where a buildup of air pressure inside the chassis causes a degradation in the airflow. Having a couple of fans pulling air into the chassis but only one fan exhausting this air can cause this effect. As an experiment, try disconnecting one of the inlet fans and see if it makes a difference.
Hope this helps,
The fans are not connected to the board's fan headers. The board has 2 fan headers, one for the front fan and another for the rear fan so i will replace my old ones with 2 fans that i can connect to the board and i will check if there is any change.
Just one last thing i want to ask you. Is there any specific feature I should be seeking for the new fans?
Thanks for all the help!
It would appear that, however you are operating these fans, their impact is inadequate. If they're inadequate at idle, image how inadequate they will be when the system is under load. For this board, you will want 3-wire chassis fans. Depending upon the mounting points provided by your chassis, you will need 80, 92 or 120 mm fans. If multiple fan sizes are supported by a mounting point, go for the largest fan size possible (the larger the fan, the more air that can be moved at any particular fan speed and (usually) the quieter it will be).