Laptop overheating until crash on Ubuntu 13.04

[Solum]

I installed Ubuntu 13.04 on my Vaio-Laptop a few weeks ago, and recently the overheating has become more and more of a problem. After half an hour it crosses 80°C, and a few minutes later the Laptop crashes and needs to cooldown before it can start again. While it is on the fan is running constantly.
I haven't found a solution by myself, so i'd appreciate your help

PC Model: Vaio VPCEB3E1E/WI
Graphics card: ATI Mobility Radeon HD 5470
Mobility Radeon HD 5000 Series
CPU: Intel® Pentium(R) CPU P6100 @ 2.00GHz × 2
Dual Core
64-bit
RAM: 4GB; 8GB maximum
Chipset: Mobile Intel HM55 Express
As far as I can tell it isn't an APU. Hybrid, not so sure.
Here are some more specs, should you want them

[QIII]

Hello!

Can you give us a little bit of information about your hardware, particularly the CPU and graphics?

[Solum]

Ah, yes. Sorry, I forgot that ^^
As far as I know there are some problems with the Mobility Radeon card drivers which cause the system to increase the temperature by 25°, but I don't really know how to fix that :/

[QIII]

That is common.

Again, though, we need some detailed information about your hardware.

What series of ATi GPU? Is this an APU? Is this an Intel/ATi hybrid graphics arrangement?

Thanks!

[Solum]

I added a link to the Laptop's webpage. You should be able to find everything there

[QIII]

OK

Have you installed the proprietary fglrx driver?

[Solum]

Yes, but apparently it doesn't support my hardware.

[QIII]

That GPU should be supported, although sometimes the M GPUs are actually just overclocked versions of earlier chips. You might find that in ATi's odd naming scheme, a 5470M is really an HD 4000 unit that is overclocked.

If you have the driver installed, could you please post the results of

fglrxinfo

[Yellow Pasque]

The 5470 is not a rebadge and should be supported by fglrx/Catalyst:
http://en.wikipedia.org/wiki/Compari...HD_5xxx_Series

[QIII]

Some of the M GPUs in the HD 5000 series are (some of them up through 5300), but in this case the chip is a Cedar so it is a real live HD 5000.