Thinkpads Forum

(Posted the below on the Lenovo forums, but thought it might be useful to readers here.)

I use my X61s as (among other things) an HTPC to play high definition videos on my TV.

I've noticed that after about 10 minutes into a high bitrate 1080p video, the CPU will suddenly throttle back to half of its maximum speed and the playback gets choppy. CPU usage when playing back 1080p is usually 45%-55%. Once the CPU speed gets throttled, the CPU has to run constantly at 100% and it simply can't keep up with some parts. (This happens even if I set Speedstep to Maximum Performance.)

These possible solutions did not work in my situation::

- Running on AC with battery plugged in (I always do this now, but still slows down)

- Adding an Evercool NB-MA1 Magic Notebook Cooling Fan to the side vent (lowers CPU temperature significantly, but doesn't stop throttling)

- Switching to 90W adapter instead of 65W (no change)

I think I've finally narrowed down this to the memory possibly overheating and throttling the whole system. I have 2 GB RAM, using two DIMMs of 1 GB each. Here's what I found:

- If I place the Thinkpad on the edge of the desk and let the DIMM cover hang over edge so it has air below it, the CPU will stay at full speed.

- If I take out one of the DIMMs (so now I just have 1 GB on 1 DIMM), the CPU will stay at full speed.

- I used to have a Dell laptop that had this exact same problem. The solution was to downgrade to an earlier version of the BIOS that wasn't as sensitive to temperature.

I'm now running on a single DIMM until I can figure out a better solution. Anybody have similar experiences with this?

I've owned many Thinkpads. I don't ever recall seeing a thermistor (or any temperature measuring device) in the RAM compartment. I don't doubt your word when you say RAM is causing this, but I'd lean more towards bad RAM vs. a problem with the X61s. It should be able to take the heat of you playing a video.

I agree with Harryc. Do both DIMMs behave the same when running alone?

I am still having this problem. Earlier I thought I solved it by removing one memory stick, but now I'm still seeing the throttling when playing videos at fairly high bitrates or high CPU usage for a sustained period of time.

I ran Memtest86+ on the DIMMs individually, several passes with no errors. I've also tested with various "CPU burning" type programs, and was able to drive up the CPU core temperatures much higher than typical temperatures without triggering any throttling.

I'm guessing now that the throttling is a result of high GPU usage (displaying large videos) or sustaining relatively high CPU load (~70%) for around two hours, or maybe a combination of the two. Maybe this triggers one of the other temperature sensors (aside from the CPU).

Any other suggestions welcome.

Install tpfancontrol (http://www.staff.uni-marburg.de/~schmitzr/donate.html). Should help narrow down what's overheating. My X61 usually seems to throttle around the 95 degree mark or so...