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View Full Version : Can the answer to some problems be as simple as a new battery??



Randolf
04-11-2005, 10:42 PM
My computer was sometimes not booting - would lock and display "insert boot disk" or similar, then would start after a couple of tries. Was going to replace power supply as is only 250W and 10amps on the 12v rail, but someone suggested try replacing the battery. Did so and computer has been fine ever since, also faster.

Maybe lots of people overlook the battery when trouble shooting. What else can a flatish battery affect??

shake_it_off
04-11-2005, 10:58 PM
Does a comp have a battery? I never knew that :lol:

Adam678
04-11-2005, 11:25 PM
It has one of those small round batteries to power the onboard clock whilst the pc is turned off, dunno if thats the battery this guy is refering to...

gibler
04-11-2005, 11:37 PM
Yeah but usually they can last for up to 10 years.
To give you an idea, some old macs that were put to use in 1999 are only now showing up with flat batteries.

You would probably notice that your date and time were always incorrect first ;)

shake_it_off
04-11-2005, 11:42 PM
Wow thats amazing..I never knew that, I'm still laughing my socks off at the fact theres a battery in a comp...easily amused? - not at all, its late :p

Elephant
05-11-2005, 01:40 AM
Wow thats amazing..I never knew that, I'm still laughing my socks off at the fact theres a battery in a comp...easily amused? - not at all, its late http://pressf1.pcworld.co.nz/images/smilies/tongue.gif

Just about to take my socks off as I do before I go to bed.
The battery fitted to the motherbard powers the BIOS.

When you power down the computer you have what do you think keeps the clock accurate?

mark c
05-11-2005, 09:15 AM
Heres a brief intro to "the battery" from Computerhope.com.

CMOS ABCs

Also known as a RTC/NVRAM or CMOS RAM, CMOS is short for Complementary Metal-Oxide Semiconductor, CMOS is an on-board semiconductor chip powered by a CMOS battery inside IBM compatible computers that stores such as the system time and system settings for your computer. A CMOS is similar to the Apple Macintosh computers PRAM.


Types of CMOS batteries - The following is a listing of the types of batteries found in computer to power the CMOS memory. The most common type of battery is the Coin cell battery (Lithium Battery) the coin cell battery is the size of a dime, as shown below.

Life time of a CMOS battery - The standard life time of a CMOS battery is around 10 Years, however this amount of time can change depending on the use and environment that the computer resides.

Randolf
05-11-2005, 01:53 PM
Yeah but usually they can last for up to 10 years.
To give you an idea, some old macs that were put to use in 1999 are only now showing up with flat batteries.

http://pressf1.co.nz/images/smilies/wink.gif

I understand the life of the battery depends on temperature, which may explain why the ones in older systems last so long. I understand a lithium battery in a laptop computer running off the mains lasts 12 - 18 mths.

As one of the battery's jobs is to keep the CMOS chip charged, and initially the battery does not die but has reduced run times, would this in turn have an effect on booting?

Graham L
05-11-2005, 02:19 PM
The answer to some computer problems can be as simple as turning the power off, waiting 1 minute, then turning it on again. That was always the first thing to do with minis, maxis, and even mainframes, in the rare occasions when "all else" failed.

It was referred to as the "Big Red Switch" repair. That carried on for the original IBM PCs, and even to the ATs, but seems to be forgotten these days.

But as usual, the term "CMOS" seems to be totally misunderstood. It refers to a semiconductor fabrication technology, not to batteries. It has the advantage that the power it consumes depends on its speed. If you have a clock crystal running at 32kHz, and a CMOS clock chip which keeps the time and date, the current used is only microamperes (or nano amperes). The Motorola clock chip IBM used to put a hardware clock in the AT happened to have 64 memory registers, which were used to hold the BIOS settings, a little more conveniently (and more cheaply) than the DIP switches and jumpers used in the previous models. Since that memory isn't being read while the computer is stopped, the memory pulls "no" current from the battery. (In fact, it was usually possible to change the cell without losing the BIOS settings).

The coin cells last a long time, though 10 years seems highly optimistic. How long does your watch cell last? That applied to the big expensive (about $43 replacement) batteries used on some early PCs, and Macs. IBM did a dirty and used a Dallas clock chip with a battery built into it in some models. They did something worse. They soldered that package in. :badpc:

Of course, nothing stays the same. Modern BIOSs use many more than 64 storage locations in the "CMOS memory". Only the 64 used and documented by IBM for the PC-AT will be the same between manufacturers. And the "CMOS memory" probably won't be CMOS RAM memory. It might be CMOS technology, but it is more likely to be NVRAM ("non-volatile") memory in a "high usage" area of the BIOS flash memory device, and it doesn't need battery backup. That's why you can't erase the BIOS passwords on some laptops by removing the lithium cell. ;)