T series overheating design fault/issue?

[JamDonut]

Hi,

Take a look at this thread in the comp.sys.laptops newsgroup:
http://groups.google.com/groups?threadm ... et.att.net
(Subject: Laptop Performance Revelation, first post date 18 September.)

To summarise, some Pentium M laptops cannot run very processor-intensive programs for a long time at full speed. The processor gets too hot and slows down to avoid damage, which can seriously impact performance. The first posting in the thread says:
[BEGIN QUOTE]
A small drop is not what's seen but a huge drop. Try on say a Sony X505 or a Toshiba Tablet doing a backup with full SW compression. I find that it
runs a 1/2-1/4 the speed of the same CPU speed system of a large format laptop or desktop.
[END QUOTE]

The sixth posting mentions having this issue with a T41p; I have pasted part of it at the bottom of this message.

Now, this raises a couple of questions for me. Do current T series laptops with Dothan CPUs still have this problem?

Dothan CPUs run cooler than the older Banias chips. The thermal design power (TDP) of Dothan Pentium Ms is 21W (1.5GHz to 2.0GHz), vs 24.5W for Banias (1.5 to 1.7GHz). [Thermal Design Power is the power which system designers should ensure the cooling system can cope with. Of course lower-speed CPUs dissipate less power. So although the TDP of the 1.5GHz Dothan is specified as 21W, the same as the 2GHz version, it should run cooler at full speed.]

Has anyone with a Dothan-based T-series Thinkpad experienced slowdown during long periods of heavy CPU use when running at full speed (from mains power)?

If so, I guess it might be worth going with a slower-than-2GHz CPU since that will run a little cooler at full speed. (The lowest speed of all Dothans is 600MHz, so if set to run at that speed when on battery power, a 1.5GHz system should perform the same as one with a 2GHz CPU. Right??)


Here's part of the sixth message from the newsgroup thread:
[BEGIN QUOTE]
Hidden is the correct term. I had it with an IBM Thinkpad T41p I bough in April this year. This nice notebook had an P-M 1.7GHz and an ATI FireGL T2 128MB gfx adapter. I notced that under full CPU load (i.e. games or professional applications) the temperature increased fastly to ~87 degree C, and the system began to throttle. The funny thing was that when I removed the DVD drive the temperature decreased around 10 degrees, and no throtteling occured. The problem seemed to be the small heatsink that covers both CPU and gfx chip (GPU), and obvioulsy didn't get enough fresh air to provide sufficient cooling.

I had some discussions with IBM about this and the under the hand confirmed that this is a known problem, that they currently have no solution, and that I have to live with that. I asked them what I should do with an 3000EUR highend notebook that's advertised as "mobile workstation" and that's unuseable for professional applications. They said I should go for the R51p which has the same mainboard and CPU but a bigger case. I asked if that means they will exchange my T41p for the R51p, and the IBM person said "No, You have to buy the R51p". I answered "fine, so I'll sell my T41p, and get a new laptop. But the new one for sure doesn't carry the IBM label any more".

I still have my old notebook, an IBM Thinkpad A31. With its new 2.2GHz P4-M CPU it gets around 47-52 degree C under full load...

> Is anyone aware of this issue and how widely spread this is?

After this problem I tested some notebooks under heavy load. The Dell I8600 doesn't have this problem, the HP nx7010, nc8000, nc800, and nw8000 also don't have this problem, too. All IBM T41p and T42p I found show the throtteling problem.
[END QUOTE]

[K. Eng]

I am skeptical of the post about the T41. The T40 series has been around for about 18 months now, and I haven't seen any complaints about CPU throttling amongst the users here.

And I think many people would have complained if the problem was widespread. Complained loudly.

After all, we complain about stuck pixels, creaking palm rests, loose batteries, flimsy plastic over the optical bay, and dim screens - things that are arguably less noticeable than a CPU that would cause the machine to get unbearably hot on the bottom.

I've had my T40 since May 2003, and even under sustained Prime95 torture test, the machine never throttled back from 1.30 GHz. IMO the fan/heatsink assembly is good enough to handle the heat output.

[JamDonut]

I am skeptical of the post about the T41. The T40 series has been around for about 18 months now, and I haven't seen any complaints about CPU throttling amongst the users here.

And I think many people would have complained if the problem was widespread. Complained loudly.

After all, we complain about stuck pixels, creaking palm rests, loose batteries, flimsy plastic over the optical bay, and dim screens - things that are arguably less noticeable than a CPU that would cause the machine to get unbearably hot on the bottom.

I've had my T40 since May 2003, and even under sustained Prime95 torture test, the machine never throttled back from 1.30 GHz. IMO the fan/heatsink assembly is good enough to handle the heat output.

I guess if there is/was a problem, it only applies to the fastest CPUs. (The original 1.3GHz Pentium M has a TPD rating of 22W, vs 24.5W for the 1.5-1.7GHz CPUs, so your machine would be unlikely to overheat.) Another factor could be the graphics chip. If that's under full load as well as the CPU, then thermal throttling will be more likely to ocur. (One of the posters mentioned that the CPU and graphics chip are attached to the same heatsink.)