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Dual Core and Heat

December 21st, 2006

Over the last few days I’ve been experiencing problems with heat in my PC. I’ve found out that dual core CPU’s run quite hot, even in an air conditioned environment.

Modern intel processors ship with a round heatsink which has a copper core. Due to this:

1. The processors integrated heat spreader (IHS) which is usually square, does not contact fully with the surface of the heatsink (which is round).
2. Due to the small area in contact, (and the fact that most intel processors generate a lot of heat), heat transfer between the CPU and the heatsink becomes a big issue - basically, for the heat to be transfered fast enough there must be remarkably good contact between the surface of the processor and the heatsink.
3. Lastly, mounting the heatsink is a complex task. I highly recommend you remove the motherboard, or mount the heatsink before you put the motherboard in the case - the reason for this is so that you can hold the board from under as you push in each of the four connectors. Doing this when the board is already installed isn’t too easy as you need to use a lot of force and risk damaging the board by flexing it.

Experiments on heat conductivity:
The importance of thermal paste

1. Heatsink affixed on processor with no thermal paste: CPU reached 87 degrees within 1 second and was shut down via bios, before throttling kicked in.
2. Heatsink affixed with generic unity plaza heatsink paste (aka toothpaste like stuff) - this worked surprisingly well under idle conditions, the cpu reached around 47 degrees. The problem occured when loading each of the two cores - at a 100% load of both cores, I recorded around 76 degrees - very dangerous and well over Intel recommended specs. (The problem with this paste is that it does not transmit heat fast enough - i.e. when idle it is capable of transmitting heat across but under full load the processor generates so much heat it simply overwhelms the ability of this paste to transfer heat.
3. Intel original heatsink thermal pad - achieved best results with an idle of 40 - 42 and maxing out at around 60 degrees - still not ideal but considering the ambient at 24 degrees approx, this wasnt too bad.
4. Intel original heatsink thermal pad  reseated - heat rapidly rose to above 70 and system was shut down for safety - this is because the thermal pad is not designed to be reused - i.e. if you remove the heatsink for any reason, clean the thermal pad fully from both CPU and heatsink, and apply a new original intel spec thermal pad! (what happens is, when you attempt the reuse the thermal material, it simply does not flow correctly over the IHS, and lumps build up leading to uneven contact.

On contacting the official intel representative, I was told that intel thermal paste/pads are not available in Sri Lanka! I.e. I gather, if someone removes their heatsink for any reason, they should buy a new heatsink with thermal pad!

Thankfully, a local Intel representative (eSys) did have the relevant replacement thermal pad on stock (Honeywell PCM 45) and were kind enough to give me 2 for free - thanks guys!

Heat and Dust*

In Sri Lanka, due to the increased ambient temperature and high amount of dust we face a few problems which include:

1. Huge amounts of dust build up in the system, blocking the fans and heatsinks (as lanetop pointed out to me) this can rapidly cripple a system. Whereas modern CPU’s include thermal throttling and other technology to protect the CPU in case of heat, many other components do NOT include any safety feature as such.
2. Ambient temperature - due to the high ambient, most components (such as northbridge/southbridge, graphics, and hard disk require EXTRA cooling).

Humidity and corrosion:

Many PC’s experience rust, due to the massive amounts of humidity in the air. This causes the following problems:

1. Connections failing - copper contacts, e.g. in memory chips start to fail causing system crashes.
2. Rust - cases/power supplies are particularly prone to this problem.

The only way to protect a PC from this is to use it in an airconditioned room/low humidity environment.

Cooling other components in your PC:

Aside from the processor, many other components are vulnerable to heat

1. Hard disk - the hard disk is extremely sensitive to heat. Operating at temperatures over 50 degrees could easily lead to data loss. Simply put if your hard disk is hotter than around 35 degrees you should use a separate fan to cool it down - you have two options here - a dedicated hard disk cooler (you can buy them at unity plaza) or simply suspend a small casing fan above the hard disk (this is a better option IMO)
   TIP: You can monitor your hard disk temperature via any software that can read the SMART output, e.g. speedfan.
2. Chipset (northbridge/southbridge)- these two chips heat up rapidly. Even if your case is well cooled, they can rapidly build up heat - the simplest solution is to install a heatsink for each (usually they come with heatsinks) and a fan if the heatsink is hot to touch.
3. Airflow through case - ensure that air flows properly through the case - ideally you should have a powerful fan at the bottom of the PC drawing air in, and a fan on top pushing air out.

Monitoring heat on your PC.

Most modern PC’s come with a number of inbuilt sensors. You can read them via free software such as Motherboard Monitor or Speedfan. I recommend speedfan as it is easier and works with modern dual core CPU’s.

Conclusions/Summary

1. Do not remove the processor heatsink - unless you have a spare thermal pad.
2. Ensure that all components in your PC are cooled sufficiently (CPU, Chipset, HDD, Graphics card)
3. Regularly clean the PC, to prevent dust build up inside, remove the case cover and use a vacumn/blower to remove the dust.
4. Use software to monitor temperatures, enable bios overheat/fan failure shutdown.

*Not a reference to M. M. Kaye’s excellent book

Entry Filed under: IT