• Some users have recently had their accounts hijacked. It seems that the now defunct EVGA forums might have compromised your password there and seems many are using the same PW here. We would suggest you UPDATE YOUR PASSWORD and TURN ON 2FA for your account here to further secure it. None of the compromised accounts had 2FA turned on.
    Once you have enabled 2FA, your account will be updated soon to show a badge, letting other members know that you use 2FA to protect your account. This should be beneficial for everyone that uses FSFT.

diff between CMOS and BIOS?

H

Hiyruu

2[H]4U
Joined
Jul 28, 2001
Messages
3,611
Isn't the CMOS the lowest level 'thing' that your computer has?

and then the second lowest is the BIOS?
 
CMOS is the chip and the BIOS is the programming written in it.
 
Listen up, sonny, and I'll tell you all about the good old days. You kids don't know how good you've got it...oh, to heck with it. It's wasn't that long ago...

CMOS is an abbreviation for Complimentary Metal Oxide Semiconductor, a technology used to make computer chips that was popular in the late 70s up through the early 90s. Two benefits of CMOS (compared to what else was available at the time) is that SRAM chips made using CMOS could hold their memory with just a small amount of energy (say, from a watch battery) and they were fairly cheap.

This was back before flash memory was affordable, and someone had the brilliant idea of using a small battery to keep a small CMOS chip powered when the system wasn't on. The chip would be used to store system settings, instead of requiring the user to flip DIP switches on the motherboard, like in the original PC/XT.

The BIOS, on the other hand, is the Basic Input/Output System, a set of low-level primative routines for booting an OS and making life easier for the OS's programmers. Certain BIOS calls needed to behave differently based on certain settings, such as drive geometry. As I said, this used to be controlled using physical switches. But, it's much more user-friendly to include a setup screen and store the values in a RAM chip...a CMOS RAM chip! :)

The BIOS has traditionally been stored on a socketed EPROM or EEPROM in PCs, so it could be upgraded by either swapping chips or reprogramming the existing one. Nowdays, the BIOS is usually stored in Flash memory which keeps its contents without an external charge and is a lot easier to program in-system than an EEPROM.

Why do we still need batteries to hold our system settings, then? Can't the system settings be stored in the Flash memory as well? There's nothing stopping it, but a true RAM chip generally has better read access times than a Flash chip (so the setup can be retrieved more quickly by BIOS routines). And, if the setup were stored in Flash, you wouldn't have the old failsafe method of pulling the battery out to reset bad system setups.

Edit: "One benefit" changed to "Two benefits"...didn't want to sound like the Spanish Inquisition there. :)
 
always wondered what the difference was, thanks for being so informative Watson2112
 
Originally posted by [Neural Interface]
thats what I call a informative, constuctive, useful post, nice one:D ;)
Click to expand...
I agree. It's worthy of being part of a 'basic hardware' FAQ :)
 
Agreed.

This should be stickied and put on the required reading list.
 
Originally posted by Watson2112
Listen up, sonny, and I'll tell you all about the good old days. You kids don't know how good you've got it...oh, to heck with it. It's wasn't that long ago...

CMOS is an abbreviation for Complimentary Metal Oxide Semiconductor, a technology used to make computer chips that was popular in the late 70s up through the early 90s. Two benefits of CMOS (compared to what else was available at the time) is that SRAM chips made using CMOS could hold their memory with just a small amount of energy (say, from a watch battery) and they were fairly cheap.

This was back before flash memory was affordable, and someone had the brilliant idea of using a small battery to keep a small CMOS chip powered when the system wasn't on. The chip would be used to store system settings, instead of requiring the user to flip DIP switches on the motherboard, like in the original PC/XT.

The BIOS, on the other hand, is the Basic Input/Output System, a set of low-level primative routines for booting an OS and making life easier for the OS's programmers. Certain BIOS calls needed to behave differently based on certain settings, such as drive geometry. As I said, this used to be controlled using physical switches. But, it's much more user-friendly to include a setup screen and store the values in a RAM chip...a CMOS RAM chip! :)

The BIOS has traditionally been stored on a socketed EPROM or EEPROM in PCs, so it could be upgraded by either swapping chips or reprogramming the existing one. Nowdays, the BIOS is usually stored in Flash memory which keeps its contents without an external charge and is a lot easier to program in-system than an EEPROM.

Why do we still need batteries to hold our system settings, then? Can't the system settings be stored in the Flash memory as well? There's nothing stopping it, but a true RAM chip generally has better read access times than a Flash chip (so the setup can be retrieved more quickly by BIOS routines). And, if the setup were stored in Flash, you wouldn't have the old failsafe method of pulling the battery out to reset bad system setups.

Edit: "One benefit" changed to "Two benefits"...didn't want to sound like the Spanish Inquisition there. :)
Click to expand...

... What he said. :D
 
I get it now.

CMOS is the hardware, and the BIOS is the software that runs on it.
 
Originally posted by Filter
still think they need the battery for the clock
Click to expand...

I agree. This is also probably why in many newer systems, you can't clear the bios settings using the good old "pull the battery" method, but rather you have to use a jumper. The memory where the bios is stored no longer requires power, so pulling the power source(which it doesn't use) won't erase it. The system clock however, *would* need power in order to keep on ticking.
 
I agree. This is also probably why in many newer systems, you can't clear the bios settings using the good old "pull the battery" method, but rather you have to use a jumper. The memory where the bios is stored no longer requires power, so pulling the power source(which it doesn't use) won't erase it. The system clock however, *would* need power in order to keep on ticking.
Click to expand...

Ok, I guess that shows how long it's been since I've had to reset my CMOS settings *blush*

You guys are right, the battery is probably just there for the RTC chip these days.
 
Originally posted by Spewn
I agree. This is also probably why in many newer systems, you can't clear the bios settings using the good old "pull the battery" method, but rather you have to use a jumper. The memory where the bios is stored no longer requires power, so pulling the power source(which it doesn't use) won't erase it. The system clock however, *would* need power in order to keep on ticking.
Click to expand...
Pulling out the battery will clear the CMOS. I think you just have to wait longer sometimes, and doing the jumper thing just discharges it faster. On some of my friends boards I didn't know which jumpers were for resetting the BIOS since two were next to eachother, so I just pulled the battery out and it worked.


still think they need the battery for the clock
Click to expand...
Isn't the clock data stored in the BIOS though?


Of course I could be completely wrong about both of these things though. :)
 
You must log in or register to reply here.
Back
Top