I think in BIOS you could only overclock CPU and RAM, but the GPU.
The problem ist the mobile version. BUT: Are you sure you want to mine bitcoins with a notebook? Even if you run a miner at GPU 750 MHz, the GPU itself becomes extremely hot. Running this for hours or days will bring your small notebook fans to max. This is not good for your ears and your hardware. If you want to mine seriously, buy a big tower rig.
BIOS is something generic: basic input/output system. All hardware has a BIOS. What you are talking about is the front end of the Motherboard BIOS.
Yes, I'm talking about motherboard BIOS. Of course you can change the ATI BIOS as well, check out my link above. But this is manual cheating in the BIOS files with flashing the chip and not just clicking around and chanage any values from BIOS GUI.
But yes, you're right.