T40 newbie and (maybe) strange question

[Robbyrobot]

Got a T40 apart for the first time today, and noted the strange chip just to the right of the (short) fan, above the ATI graphics chip and the two (presumably) graphics RAM chips. It looks for all the world like a CPU - with a die in the center - but has no heat sink or fan attached. As far as I can tell, it's a BGA chip.

This may be obvious to people who have experience, but can anyone explain?

[FTC]

Hi,

This is the northbridge.

Current PCs have two other important chips besides the CPU and the GPU : The northbridge and the southbridge. These aggregate most of the 'simpler' functions of the motherboard together. Normally the northbridge is the one that 'talks' directly to the CPU and deals with high-speeed buses, such as the RAM memory bus and/or AGP. The southbridge manages normally the lower speed buses such as the PCI / ISA, IDE / SATA, LAN. USB, AUDIO,...

Note that the southbridge is located under the wireless m-PCI card on thinkpads T4x, and also 'looks' like the northbridge .."like a CPU".

[Robbyrobot]

Interesting... but how are such chips cooled? Assuming they get hot at all. From the appearence, I would have assumed they need a heatsink or something of the sort. The similarity with a CPU is confusing me.

[richk]

They are made to run as-is. The machines with the optional, high-performance graphics chips use a long fan that contacts the GPU, but the northbridge and southbridge chips use nothing.

[Robbyrobot]

Note that the southbridge is located under the wireless m-PCI card on thinkpads T4x, and also 'looks' like the northbridge .."like a CPU".

Yes, I see it, but the appearance is completely different... just a black ceramic package. The thing that was throwing me was the blue die in the center of the green PCB of the chip I mentioned.

At any rate, many thanks for the help!