to clear CMOS

  • Thread starter Thread starter ML
  • Start date Start date
M

ML

I understand that I need to unplug the computer first when moving the jumper
from the original pin position to pins 2,3.
Now that the jumper is in the 'clear CMOS' pins, for how long should I power
up the computer before shutting down to replace the jumper to its original
position?

The manual didn't state this clearly.
Thank you.
 
ML said:
I understand that I need to unplug the computer first when moving the
jumper
from the original pin position to pins 2,3.
Now that the jumper is in the 'clear CMOS' pins, for how long should I
power
up the computer before shutting down to replace the jumper to its original
position?

The manual didn't state this clearly.
Thank you.
Click to expand...

Normally it is instantaneous on the powerup but every motherboard
manufacturer may be different so YMMV. Every time I have ever had to clear
the CMOS it was power off, change pin position, power up, power down after
about 1 second, change pin position, power up.
 
Thats only part of it,after unplugging,remove the battery,then move pins
from 1-2 to 2-3,move for .25 seconds or so,then back to 1-2 position,replace
battery,start pc,open BIOS & reset it,as it will have loaded all settings
to "As
it came from mfg".
 
ML said:
I understand that I need to unplug the computer first when moving the jumper
from the original pin position to pins 2,3.
Now that the jumper is in the 'clear CMOS' pins, for how long should I power
up the computer before shutting down to replace the jumper to its original
position?

The manual didn't state this clearly.
Thank you.
Click to expand...

The procedure differs from product to product, and if someone quotes
a procedure here, without knowing the system, your system could be
damaged.

For what it is worth, on the machines I have here:

1) Power off and unplug.
2) Move Clear CMOS jumper to the alternate position.
3) Wait ten seconds.
4) Move Clear CMOS jumper back to the original position.
5) Only apply power to the system, when the jumper is in the original position.

The reason for this procedure, and warning, has to do with
the bad design concept used on some, but not all, computers.

There are two power sources feeding the CMOS/RTC. There is
a source based on the ATX power supply +5VSB source. And
there is the CMOS battery, as the backup source. Some
CMOS clearing designs, short that power to ground. That
can burn or damage the dual diode (logical "OR") device,
that accepts power from either source. If +5VSB is
present, when the shorting jumper is used, one of the
diodes in the three pin package is damaged. And that
can have an impact on the BIOS being able to remember
settings later and so on. I've helped at least one
poster to repair that, by installing replacement
discrete diodes.

So that is the origin of all this "power off" business.

Some chipsets take a different approach, and provide a
proper logic signal for clearing CMOS. With that design,
you could manipulate the jumper at virtually any time,
without concern.

But in the interest of preventing accidents, the prudent
practice is to unplug the computer before doing the procedure.
There are many older computers, that have the bad design
present.

Not that many years ago, it wasn't uncommon for the
instructions in the user manual to be just plain
wrong. So some systems were damaged in the past, because
people actually read the instructions. An "insert sheet" in
PDF format, was provided on the manufacturer web site, or
in some cases, they did nothing to correct the situation.
In 2009, I would expect this is largely a thing of the
past.

So before doing anything, I would

1) Acquire a copy of the manual.
2) Google on the make and model, to see if "anybody got burned"
by following the instructions.

I usually try to clear CMOS the first time, by following
the instructions. If I start the computer later, and the
RTC clock did not get reset, I may repeat the procedure.
But this time, I might remove the CR2032 battery from its
socket for a minute, while the jumper is being used. But
rather than have that battery flopping around, for a first
attempt, I might just leave the battery in place. Removing
the battery, is for cases where the computer appears
to be "stubborn".

1) Power off and unplug.
1a) Remove CMOS battery.
2) Move Clear CMOS jumper to the alternate position.
3) Wait ten seconds.
4) Move Clear CMOS jumper back to the original position.
4a) Reinstall CMOS battery
5) Only apply power to the system, when the jumper is in the original position.

Paul
 
ML said:
I understand that I need to unplug the computer first when moving the
jumper
from the original pin position to pins 2,3.
Now that the jumper is in the 'clear CMOS' pins, for how long should I
power
up the computer before shutting down to replace the jumper to its original
position?

The manual didn't state this clearly.
Thank you.
Click to expand...

You also need to remove the cmos battery. Power down, unplug, remove the
battery, short the pins, count to 10, move the jumper back, put the battery
back, plug back in and reboot.

Often you cannot start a system at all with the CMOS CLEAR jumpers shorted.

HTH
-pk
 
ML said:
I understand that I need to unplug the computer first when moving the
jumper
from the original pin position to pins 2,3.
Now that the jumper is in the 'clear CMOS' pins, for how long should I
power
up the computer before shutting down to replace the jumper to its original
position?

The manual didn't state this clearly.
Thank you.
Click to expand...


With the machine powered OFF, move the CMOS jumper to pins 2 and 3..

Now move the jumper back to pins 1 and 2.

Power up the machine, and go into BIOS to reset the date and time, and any
other settings which you personally prefer.

There is no need to remove the battery, or wait more than the time it takes
to move the jumper..
 
Mike Hall - MVP said:
With the machine powered OFF, move the CMOS jumper to pins 2 and 3..

Now move the jumper back to pins 1 and 2.

Power up the machine, and go into BIOS to reset the date and time, and any
other settings which you personally prefer.

There is no need to remove the battery, or wait more than the time it
takes to move the jumper..
Click to expand...
On my Asus board, the battery MUST be removed (as the manual states) in
order to clear it. If I only move the jumper, not all settings are reset. I
found this out for a fact less than 2 weeks ago when a BIOS flash went bad.

SC Tom
 
SC Tom said:
On my Asus board, the battery MUST be removed (as the manual states) in
order to clear it. If I only move the jumper, not all settings are reset.
I found this out for a fact less than 2 weeks ago when a BIOS flash went
bad.

SC Tom
Click to expand...


OK.. ty.. do you know which settings are not reset?
 
SC Tom said:
On my Asus board, the battery MUST be removed (as the manual states) in
order to clear it. If I only move the jumper, not all settings are reset.
I found this out for a fact less than 2 weeks ago when a BIOS flash went
bad.

SC Tom
Click to expand...


I looked at the Asus manual for the M3N78-VM, a board which I recently built
into a new system. It states that moving the CMOS jumper should clear the
settings but, if it doesn't for some reason, the battery should be pulled
too. I have always found that the jumper alone does the job..
 
Mike Hall - MVP said:
I looked at the Asus manual for the M3N78-VM, a board which I recently
built into a new system. It states that moving the CMOS jumper should
clear the settings but, if it doesn't for some reason, the battery should
be pulled too. I have always found that the jumper alone does the job..
Click to expand...

Mine's the M2NPV-VM and it clearly states on page 1-20, step 2 to "Remove
the onboard battery." If you'd like to see for yourself, go here:
http://dlsvr.asus.com/pub/ASUS/mb/socketAM2/M2NPV-VM/e2527_m2npv-vm.pdf

SC Tom
 
Mike Hall - MVP said:
I don't doubt that it does. Looks like Asus can't make up their minds..
:-)
Click to expand...

My guess is that on the newer boards, the jumper bypasses the battery
completely (or more so than on the older boards) making it unnecessary to
pull the battery. Engineering, you know- "If it ain't broke, redesign it!"
I was looking at the board you have as an upgrade, but it only has one EIDE
channel, and unfortunately, I still have 3 EIDE devices that I'm not ready
to part with. I really don't NEED to upgrade (my AMD 64x2 Dual 4800+ is
plenty fast), but every once in a while I get that need for speed. Not
having a larger income kinda curbs that feeling, but it's still there :-)

SC Tom
 
SC Tom said:
My guess is that on the newer boards, the jumper bypasses the battery
completely (or more so than on the older boards) making it unnecessary to
pull the battery. Engineering, you know- "If it ain't broke, redesign it!"
I was looking at the board you have as an upgrade, but it only has one
EIDE channel, and unfortunately, I still have 3 EIDE devices that I'm not
ready to part with. I really don't NEED to upgrade (my AMD 64x2 Dual 4800+
is plenty fast), but every once in a while I get that need for speed. Not
having a larger income kinda curbs that feeling, but it's still there :-)

SC Tom
Click to expand...


It isn't my board and I built it for somebody else. My production machine is
a single core 939 running a 3500 +.. :-(

The M3N78VM is ok but I do not like the video port arrangement. The DVI port
is firmly fixed to the board, but the VGA port is soldered on behind it and
is prone to flexing. Fortunately, the clients monitor has DVI connection,
but it is definitely a negative feature.
 
SC Tom said:
My guess is that on the newer boards, the jumper bypasses the battery
completely (or more so than on the older boards) making it unnecessary to
pull the battery. Engineering, you know- "If it ain't broke, redesign it!"
I was looking at the board you have as an upgrade, but it only has one
EIDE channel, and unfortunately, I still have 3 EIDE devices that I'm not
ready to part with. I really don't NEED to upgrade (my AMD 64x2 Dual 4800+
is plenty fast), but every once in a while I get that need for speed. Not
having a larger income kinda curbs that feeling, but it's still there :-)

SC Tom
Click to expand...


Gentlemen:
I've worked with a considerable number of makes/models of motherboards over
the years and I really can't recall a single instance where it was necessary
to remove the CMOS battery in order to reset the CMOS-BIOS settings to their
factory defaults when the motherboard was equipped with a CMOS jumper. In
every case that I've experienced it was only necessary to short the jumper
to reset the CMOS-BIOS values.

As I'm sure you both know, many motherboards (particularly early types) were
not equipped with a CMOS jumper so obviously the only way to carry out the
preceding was to remove the CMOS battery for some seconds and then replace
it.

I understand SC Tom's reference to that ASUS MB instruction indicating the
need for also removing the CMOS battery in addition to shorting the CMOS
jumper. All I can tell you is that it isn't the first time (and I'm
confident it won't be the last time!) that a motherboard's User Manual (let
alone technical advice from the manuf. itself!) provided misleading or
outright incorrect info re their products & their use. Although I have to
quickly add that our advice to users is virtually *always* follow the
instruction(s) in the motherboard's User Manual/Guide.

Anyway, having said all this and notwithstanding my own experience re this
CMOS battery issue, I learned a long time ago that when it comes to PCs,
*anything* is possible.

So SC Tom...assuming you haven't already done so, have you tested to
determine whether simply shorting the CMOS jumper without removing the CMOS
battery will reset the time/date info & BIOS configurations?

Incidentally, re your refererence to the fact that your motherboard has only
a single IDE channel...
Are you aware that some of the newer (usually the higher-end ones)
motherboards are now coming through without *any* IDE channels? And more &
more motherboards - are equipped with only a single IDE channel. As the
youngsters say, "SATA rules".
Anna
 
Replies embedded towards the end. . .

Anna said:
Gentlemen:
I've worked with a considerable number of makes/models of motherboards
over the years and I really can't recall a single instance where it was
necessary to remove the CMOS battery in order to reset the CMOS-BIOS
settings to their factory defaults when the motherboard was equipped with
a CMOS jumper. In every case that I've experienced it was only necessary
to short the jumper to reset the CMOS-BIOS values.

As I'm sure you both know, many motherboards (particularly early types)
were not equipped with a CMOS jumper so obviously the only way to carry
out the preceding was to remove the CMOS battery for some seconds and then
replace it.

I understand SC Tom's reference to that ASUS MB instruction indicating the
need for also removing the CMOS battery in addition to shorting the CMOS
jumper. All I can tell you is that it isn't the first time (and I'm
confident it won't be the last time!) that a motherboard's User Manual
(let alone technical advice from the manuf. itself!) provided misleading
or outright incorrect info re their products & their use. Although I have
to quickly add that our advice to users is virtually *always* follow the
instruction(s) in the motherboard's User Manual/Guide.

Anyway, having said all this and notwithstanding my own experience re this
CMOS battery issue, I learned a long time ago that when it comes to PCs,
*anything* is possible.

So SC Tom...assuming you haven't already done so, have you tested to
determine whether simply shorting the CMOS jumper without removing the
CMOS battery will reset the time/date info & BIOS configurations?
Click to expand...


As I replied to Mike, yes, I did try just using the jumper to clear the BIOS
and some settings were not reset. To list a few settings that were not reset
to BIOS default were:
Boot order
Onboard NIC not re-enabled
Onboard sound not enabled
Parallel port not enabled
Ability to boot- not enabled.

Granted, part of this might have been caused by the bad flash, but after
removing the battery, then changing the jumper, changing it back, and
reinstalling the battery, all was well and the settings were back to factory
default.

Having worked on and with computer hardware since the mid-60's when I was in
the Air Force, I realize that most manuals add things that aren't necessary,
leave out things that are necessary, or are blatantly incorrect. And it is
most certainly not relegated only to the electronics field. Try a shop
manual for any vehicle sometime. It's easy to get hurt if you take them as
gospel.


Incidentally, re your refererence to the fact that your motherboard has
only a single IDE channel...
Are you aware that some of the newer (usually the higher-end ones)
motherboards are now coming through without *any* IDE channels? And more &
more motherboards - are equipped with only a single IDE channel. As the
youngsters say, "SATA rules".
Anna
Click to expand...

Yes, I realize there are lots of SATA-only MB. I just mentioned the one that
Mike used because it was one of my choices if I did decide to upgrade. All
things considered, I decided to stay with the one I have since it performs
well enough for me (so far ;-) ).
BTW, mine has 2 EIDE and 4 SATA channels.

SC Tom
 
"Having worked on and with computer hardware since the mid-60's when I was
in

the Air Force, I realize that most manuals add things that aren't necessary,
(Etc.)



I still remember one joint service communication device from my Navy
(Vietnam Era) days. Seems that the manual had deliberate errors, which were
intended to disable the device if an unqualified person attempted to
troubleshoot or repair the device. A somewhat mildly interesting story or
two were related to this equipment.

I had a motorcycle that I had stored in an out of the way storage area that
contained copies of manuals for equipment that I repaired. We were in
Vietnam, and a device failed, dud to a bad circuit board with no onboard
spare. I could only take the board to a nearby repair facility for exchange
if I had my own transportation--no hitch hiking allowed, and no walking or
bus ride either.

Since the ship was too small to carry it's own jeep or small truck, there
was an impasse. I mentioned to the Captain that there was a possible
solution if he allowed me to provide transportation, and afterwards restore
everything to "as it was".

(He didn't know that I had a motorcycle hidden away) Next scene- I'm going
down a road on the motorcycle, in Vietnam, in dungarees, with a navy issue
revolver in a shoulder holster. The motorcycle had Japanese Plates. The MP's
at an intersection were somewhat upset, since US military stationed in the
area were not allowed to have motorcycles. When I told them where I was
going, and in general terms what I was carrying, problems went away.

Another tale had to do with the Pueblo's capture. We had to ship the device
to a US location and have it modified. The comm officer, myself and two
radiomen obtained a closed truck from a navy motorpool to carry the device
to a "secure" shipping point. When we arrived at a navy base gate, the
guards asked for paperwork showing where we were going. (We had the
authorization papers to use the truck, but our destination and route were
left open by intent.) One gate guard decided that he was going to open the
door on the rear of the truck to see what we had inside.

What was inside was the equipment, double packed in a crate. One of the
radiomen was sitting on top of it. He had been told that if someone
attempted to open the door without us telling him it was OK, He might have
to actually use the Thompson that he had been given.

Gate guard opens door, and is met with the radioman cocking the machine gun,
as he points it at the guard's face. (OOPS!)
 
SC Tom said:
On my Asus board, the battery MUST be removed (as the manual states) in
order to clear it. If I only move the jumper, not all settings are reset.
I found this out for a fact less than 2 weeks ago when a BIOS flash went
bad.

SC Tom
Click to expand...

I hear where you're coming from, and have seen it myself. After some
thought on the subject I can see how circuitry could be designed where the
battery in place could have kept the cmos memory powered when the CLR CMOS
jumper is utilized. And, the reverse scenario as well by removing the cmos
battery and not using the CLR CMOS jumper. Hence, one would have to use
both. So, I tend to agree with you. To top it off, its not a big deal to
remove the cmos battery AND use the CLR CMOS jumper as well. Surely, no
harm is done regardless. So, I don't understand the subsequent negative
responses being needed at all. Keep sending your experiences as that what a
newsgroup is for, sharing information.

As for what data may be held after using the CLR CMOS jumper is utilized and
then placed in normal position, the data the previous bios assessed for
hardware in a botched up sort of way. The newer flashed bios may be
addressing different cmos addresses for that same data, it will only see
garbage and can go no further. That is in the case where the cmos battery
not removed has an effect on the cmos portion for that data. My 2 cents.
 
Mr. Smith said:
Why ask here? This has nothing to do with WinXP.
Click to expand...

Ignore the resident ****wit. Your question is welcom as the responses
should indicate.

"Mr Smith" is a mentally retarded school child who has delusions that he is
some sort of self appointed newsgroup moderator who can decide what you can
post and what you can't.

He isn't.
 
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