And how do you access it? Because i've never heard of one!

What would you want to do in said BIOS? Whatever you want is probably in the System Preferences.

Like how can you OVerclock? I heard you can do that in some BIOS'S

Sorry tohaaaa I don't know and I couldn't find any thing on how to overclock a mac using Google.

BIOS's have nothing to do with an operating system - so just like Windows, Linux, and every other OS in the world don't "have" a BIOS, neither does OS X. What you probably mean to ask is whether or not Mac's have BIOS's - in which case no, they don't. PPC Macs have what's called "OpenFirmware" while Intel Macs use EFI.

Well if you want to overclock, I first off, wouldn't recommend it and second, there are programs which will ask you for your password and let you control variables that you would like to overclock. The BIOS however is a feature that comes on the motherboard and not the system it self. PCs without a HDD have a functional BIOS.

You can launch an EFI shell on booting a Mac, with either the stock EFI or rEFIt. I prefer rEFIt since I don't have to hold Option to launch Bootcamp.

The BIOS is a specific type of Firmware. Macs (not Mac OS X) have a firmware called EFI. EFI was initially created by Intel for the IA64 (Itanium) architecture. It is considered the next generation firmware also for 32 and 64 bit x86 architectures, though most non-Apple implementations are built around version 2.0 of the EFI specification (now known as UEFI). EFI provides a lot of advantages compared to the BIOS, that can be found by seeing the wikipedia page.

Regarding the BIOS in Macs, there is also such a thing, but differently implemented. There is a CSM (Compatibility Support Module), which is a special kind of payload (EFI application if you want) which emulates a system BIOS and a video BIOS for legacy operating systems. While technically not accurate, you can think of it as a mini-VMWare running in EFI mode. So, especially for Windows XP, 2003 and 32-bit Vista and 7 you have an emulated BIOS.

Since Apple computers implement a mix between UEFI 2.0 and EFI 1.1, they are not compatible with Windows 7 in UEFI mode. Windows 7 and Windows Vista SP1+ require a UEFI 2.0 compliant system to run in UEFI mode. Thus, on Apple computers, the EFI is useless in Windows and only the CSM is used. However some other vendors have UEFI 2.0 compliant systems (just not Apple compatible out of the box).

Getting back to the purpose of your question regarding over clocking and fine-tuning. The Mac EFI allows you to customize it by two ways:

1. Write an EFI application that does exactly what you want (over clocking or others). Not something that most people might consider the first option though.
2. Using the NVRAM from the OS. The Mac EFI allows you to change a few variables, as follows (mid-2010 mbp):
   
   • efi-boot-device (the default boot device)
   • efi-boot-device-data (parameters for above)
   • gpu-policy (the implicit settings for switching between integrated and discrete video card)
   • BootCampHD (what partition is to be used for the CSM)
   • SystemAudioVolume (what audio volume was last setup in the OS, so that the startup sound doesn't blow the roof off)
   • prev-lang:kbd (What language is the keyboard in)
   And probably a few others.

In conclusion, it's highly unlikely that you can over clock using EFI. Though there are a few Mac applications that allow you to manage the CPU and FAN speed. The Mac doesn't use a BIOS, it has an EFI firmware, however it emulates a very basic BIOS.

Sorry for the bad news.

Ahhh Well that sucks Can someone give me a program that can control said variables?

And if you're running OS X on a PC, that still has a BIOS. The bootloader, started by the BIOS, emulates EFI to boot the OS

How would I access said EFI?

you can modify the efi from the OS with certain apps

WHat Apps are these?

cant remember the apps name but the are many, try google. I am sorry at the moment i working with 7850 and have no hazard hackingtosh installed at the moment. I am without snow leopard at the moment. I have modified the efi string for my graphics card and for me I see altering the efi quite complex and easy to get the panic screen

looking at the kind of questions you're asking here, it seems you have no idea what you're talking about, therefore please forget about overclocking...

Just because I don't know what apps to download does not mean I do not know what i'm talking about

Hey we all forget apps sometimes. I have a friend who had been working with a simulation program for over 5 years and I asked him what it was and he couldn't remember for a couple hours. We all forget. That's the beauty of the human brain.

It does, its practically inaccessible anyway but yes every machine to my knowledge has a bios which is essential to functionality pretty much

not knowing the name of an app is one thing, not knowing the difference between the firmware and an OS is another

darn I thought BIoS was part of the OS *FacePalms*

Incorrect. Macs simply don't have, and never have had, a bios.

Not by name but functionality they have UEFI.

You will never be able to OC your mac, so i suggest you stop trying now.

Overclocking a Mac is possible but it is much harder then in a PC. Now I am almost always against people who tell you to stop, but if you have no clue what you are doing, I suggest you don't try it because overclocking involves changing various variables that can burn out your CPU, GPU, and other peripherals needed by the computer.

Ok thanks for the warnings But No ones really given any real info on how to over clock a mac!

Maybe if someone can point me to a list of applications that will help me achieve my goals