I'm asking for suppor for my issue: I have an old Toshiba laptop (Satellite SM30-604) with mobo Intel odem i855pm-333.
There are 2 fan cooling cpu and they are doing their job very vell. Unlikely, no one is connected to the mobo. So, when cpu reaches 70°C (it's a centrino cpu 1600 MHz, so 70°C it's a standard temperature), the mobo can't "activate" the fan (in fact the fan is olready working, but the mobo doesn't know) and, for this teason, the mobo slow down CPU speed to a quarter.
Question is: there is a bios upgrade/mod to disable fan or temperature check/control?
First, verify the model number. I didn't see that model on Toshiba's website. Once you verify, I suggest you go to toshiba.com and look for your model in their tech support section. You should then be able to determine if there is a more current BIOS update fro your system.
However, I would be very surprised if a laptop BIOS would allow you to disable the fan control. If your current BIOS doesn't allow it, an updated version isn't likely to add that capability.
Finding a modded BIOS for a laptop, especially an older system, is likely to be fruitless. I wouldn't spend too much time seeking this sort of solution as it simply, likely doesn't exist.
You can try a couple of things. Re-flash the BIOS with the most current version, even if you already have installed. This will sometimes correct issues that are BIOS related.
Also, because notebooks/laptops are so integrated (everything is built into the motherboard) and any sensor or control issues associated with the problems you are experiencing are resident in the motherboard, you might consider buying a replacement motherboard. I am sure you can find replacement parts via eBay or at one of the many notebook parts recycling sites.
My guess is that you have a defective temp sensor and it is causing the issue you are seeing. You could also download speccy (piriform.com) to potentially isolate the wonky sensor and speedfan (http://www.almico.com/speedfan.php) to see if you can force the fans to stay on all of the time.