I have experimented during the week with reducing the maximum processor speed in order to cool my fully loaded X61 7764 Tablet and preventing it overheating and shutting down.
a) EXPERIMENT 1: Reducing the CPU speed to keep the machine cool.
b) EXPERIMENT 2 : Using an external fan to cool the machine
EXPERIMENT 1: Reducing the CPU speed to keep the machine cool.
Symptom:
During heavy IO activities the machine will heat up and spontaniously shutdown. For example during application installs, iPod synchronization, iTunes podcast downloads, playing video and system backups. The symptoms became noticable after updates in early May though it may have failed with some long video playbacks prior to that.
Method:
Each time the system failed I reduced the maximum CPU speed on the balanced profile by a further 5% in order to find a level at which different operations are stable. The laptop was on an Ultrabase, has 2Gb ram, a 4Gb SD Card with 3.5Gb ReadyBoost, Intel Turbo Memory, 5400 RPM drive and 95W adaptor (The behaviour was the same with the prior 65W adaptor).
The balanced mode was set to continue with balanced during indexing and search operations.
Findings:
Between 90% and 40% iPod synchronization seems more likely to not cause a shutdown the more you slow the CPU.
At a maximum of 35% of full CPU speed it is possible to backup the machine image to a network drive. At faster CPU speeds backups will cause the machine to overheat within 25 minutes (Test repeated three times at 40%)
At 30% it is possible to complete backup of an image to a faster USB drive (Which requires more frequent IO and will fail at 35% of CPU). At 30% of CPU QT HD video can be played for up to 20 minutes before overheating causes a shutdown.
Conclusions:
Slowing the CPU does noticably cool the machine and allows a wider range of functions to complete to the point where at 30% maximum CPU speed the machine is acceptably stable. The fact that the CPU has to be slowed to this extent to produce sufficent cooling indicates that much of the heat is coming from something else. Possibly the Hard Disk as this is also involved in the IO operations showing the symptom. It wouldn't appear to be excessive graphics related heat as video and non video operations cause overheating.
EXPERIMENT 2 : Using an external fan to cool the machine
Method:
Purchased a small room fan (10 Inch personal box fan) at a local pharmacy/supermarket. Placed the fan to the right of the X61 Tablet facing slightly down so that it was blowing from right to left (The same direction as the internal fan so as to be assisting not working against the internal fan). The fan is directed at the right side of the machine, palm rest and keyboard from a range of six inches. If desk mounted rather than on an UltraBase then flow along the desk and under the machine would have assisted. The tests were performed with the laptop on an UltraBase which is a worst case condition as the UltraBase almost fully blocks all under side vents. The cost of the fan was $15.
Result:
The fan signficantly cools the machine. The palm rest is cool to the touch even at 100% of CPU. The top of the VGA socket on the left of the machine (Not directly receiving air) is noticably cooler and is only warm to the touch. All operations including playing extended video and backing up to a local USB drive can be achieved with 100% CPU. At 100% the palm rest will become warm while hands are typing but when hands are away from the keyboard it is cool. This is fine as typing operations are not what strains the system and continuous resting of the palms for over twenty minutes is likely to be rare. It cools within two or three minutes and never reaches extreme temperatures with the fan in place.
Conclusion:
It can be no surprise that active cooling works. The boxed fan offers a noisy, inconvenient, non portable temporary solution with full system speed but when mobile it is necessary to switch to a power profile with a maximum of 30% of CPU speed and no override power profile for search and indexing. Longer term internal use of an X61s second fan 42X3806
http://i10.tinypic.com/66etkq1.jpg via a custom power cable (Not all X61 models have the power connector) is probably the most practical long term solution unless a software update or other hardware solution is forthcoming from Lenovo. Until then the fan and power profile are the best workarounds. The 30% CPU restriction is not as harmful as you would expect to the overall system experience.
It is of course pointless to argue that none of this should be happening to us or that the updates in May shouldn't have had this effect. For some unknown reason they did so the best thing is to adopt some workaround and just make sure people are aware of the problem and hope that sufficient people are affected by it for the vendors (Lenovo, Microsoft, Intel) to track the issue down and offer an available solution, such as a cable for the second fan being used to retrofit the fan, or being available as a part.
The external box fan will definitely keep you and your colleagues awake at your desks in the interim!
Message Edited by hiker on
05-26-2008 06:44 PM
