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CPU TDP does not explain actual power consumption?

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May 8, 2014 1:58:33 PM

Hi, I tried to install a i7-3612QM to my thinkpad t430 (installed with i5-3210m) with 65 Watt Power Adapter. First, I removed the battery, and when I powered up the laptop and booted into the OS, everything is fine. Second, when I installed the battery back on, and booted the laptop, got into the OS, and the lenovo power manager popped up a message saying the current Power Adapter can not supply enough power to the laptop and suggested buying a bigger one. Now, both CPUs have TDP of 35Watt, so I am wondering is it the real figure, and I searched the internet, but somehow, CPU Boss indicates that both CPUs have the same typical power consumpation of 28.44Watt. So I am completely confused by now. What is happening?

cheers
a c 77 à CPUs
May 8, 2014 2:04:02 PM

TDP is Thermal Design Power. It is the rated power consumption/output of any given integrated circuit. It can exceed this value as well as stay below this value.

You should try the latest version of the power manager. We had many issues with the first few revisions Lenovo provided our company.

Might try a firmware/BIOS update if that does not resolve it.
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a c 174 à CPUs
May 8, 2014 5:33:39 PM

daiyue said:
Hi, I tried to install a i7-3612QM to my thinkpad t430 (installed with i5-3210m) with 65 Watt Power Adapter. First, I removed the battery, and when I powered up the laptop and booted into the OS, everything is fine. Second, when I installed the battery back on, and booted the laptop, got into the OS, and the lenovo power manager popped up a message saying the current Power Adapter can not supply enough power to the laptop and suggested buying a bigger one. Now, both CPUs have TDP of 35Watt, so I am wondering is it the real figure, and I searched the internet, but somehow, CPU Boss indicates that both CPUs have the same typical power consumpation of 28.44Watt. So I am completely confused by now. What is happening?

cheers


TDP is the manufacturers rated power consumption under heavy, non-synthetic operating conditions. Synthetic operating conditions such as the Intel Burn Test benchmark can cause the power draw to exceed the TDP.

TDP is used by manufacturers to both gauge how much electrical power needs to be delivered to the device, as well as design a cooling apparatus for the same device.
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a c 199 à CPUs
May 8, 2014 5:44:05 PM

TDP is done in buckets, it is not an exact value of how much you will consume, but instead a value of the maximum you could consume with that silicon. Intel seems to have a bunch of TDP buckets going on for mobile right now with haswell CPUs, but Sandy Bridge mobile chips were all 17/25/35/45/55W chips, so if most i5-3210m only consume 23W but there is some variance that might result in them being 26W chips, then they get tossed up a bucket and marked as 35W chips even though there is no way that a chip at that clock speed will ever use 35W, but since it exceeds the 25W bucket it has to be listed as the next one up. While the i7-3612QM may normally consume 32W of power at full load resulting in a notably higher power draw than the i5 which is the same listed TDP.

It is also important to note that the CPU is only about half the power draw of a laptop, so you were likely already running at 50W before the CPU upgrade, you are likely pushing the limits of the charger especially if you throw screen brightness to full.
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May 9, 2014 7:36:30 AM

hunter315 said:
It is also important to note that the CPU is only about half the power draw of a laptop, so you were likely already running at 50W before the CPU upgrade, you are likely pushing the limits of the charger especially if you throw screen brightness to full.


and so the power adapter could not handle it and then the power supply switched to battery. This is exactly what happened when I installed battery back on and booted the laptop. The laptop was using battery power and the screen went darker.
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