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Boot without CMOS battery?

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  • Motherboards
  • Battery
  • Boot
  • CMOS
Last response: in Motherboards
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April 16, 2011 12:09:32 AM

Building a PC. MOBO came without a battery in the CMOS battery holder. Board does not pass POST. No beep of any kind. Is the lack of a battery sufficient to cause it not to boot? A low battery would mean the CMOS values are not persistent…but no battery?? Fans and standby power LED function normal.


I have it stripped down to just this( I read the guide):
MOBO: ASUS M4A87TD EVO
CPU: AMD Phenom II X4 955
PSU: Zepher MX 750


ASUS is sending out a battery.

If adding the battery is all that is needed then I can wait. MOBO is in chassis. If it should boot with out the battery then I can pull it out and retest in the breadboard type configuration. I’d rather not remove it if I am just playing the waiting game. But if the battery does not matter I want to find out what part is bad to start the RMA.

Any help is appreciated.

More about : boot cmos battery

a b V Motherboard
April 16, 2011 12:12:48 AM

Bad news for you, not having the battery in does not stop the computer from booting. I would start the RMA procedure or bet yet figure out what you have done wrong.
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April 16, 2011 12:51:57 AM

That’s what I was afraid of.

Now what to do to narrow it down between the PSU, CPU or MOBO?


On the above set up I probed some unused connectors:
On the molex connector (R, B, B Y):
Red = 4.98V
Yellow = 12.04V
On PCI-E connector (B, B, B, Y/B, Y, Y/B)
Yellow/Blue = 12.07V
Yellow = 12.06V
Yellow/Blue = 12.06V
On 4pin CPU (B, B, Y, Y)
Yellow = 12.06V
Yellow = 12.05V

Once I pull it out an can look at the 24 pin connector.

I believe that I am down to how to decide between the CPU and MOBO. I’m not sure how to proceed there.

I have had a ground strap to the chassis during the build. So the parts should be good ESD wise.

If the breadboard set up has the same results what’s next?
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a c 158 V Motherboard
April 16, 2011 1:13:20 AM

Yeah, the battery only remembers BIOS changes.

I'm trying to remember the MINIMUM you can add to a motherboard for tests. Actually, I believe you can run some diagnostics with NOTHING BUT THE PSU attached.

You'd have to see your motherboard diagnostics info but you may have a bad motherboard.

Where did you buy it? The fact that a battery is missing makes me wonder if somebody snuck in a defective motherboard. I've gotten bad components before (I even got an old hard drive from Futureshop that someone snuck in a new box.)
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a c 117 V Motherboard
April 16, 2011 1:31:53 AM

You'll need ram and a cpu to post.
Hdd and OD are not required.
And of course a psu.
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April 16, 2011 6:11:03 AM

I have RAM. I just had the bare minimum set up to get post failure beeps. MOBO does not seem to be getting that far.

Bought from Newegg. It does seem like a big part to get past QC.

Also, I removed the mobo from the chassis and retested with same results.

I'm stuck not knoing how to run any mobo diagnostics. So it looks like a return for me.

When I do return I will have to remove the CPU. That mean removing the HSF and breaking the thermal connection. When I do put the CPU in another mobo can I just reattach the HSF with the existing thermal compound? Or do I have to go through the hassle of cleaning and reapplying.
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April 16, 2011 6:39:54 AM

Hmmm.... maybe a knock off gucci will solve my problem. Brilliant!!






(insert KobeBryant like slur directed at previos post)
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a b V Motherboard
April 16, 2011 9:47:45 AM

When refitting a heatsink you should always go through the hassle of cleaning the heatsink and reapplying the heatsink compound. I know people who don’t do this and they wonder why their temperatures are high and their computer unreliable.
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a c 156 V Motherboard
April 16, 2011 12:45:02 PM

photonboy said:

I'm trying to remember the MINIMUM you can add to a motherboard for tests. Actually, I believe you can run some diagnostics with NOTHING BUT THE PSU attached.

True.

davcon said:
You'll need ram and a cpu to post.
Hdd and OD are not required.
And of course a psu.

To successfully POST, you also need a video card or on-board GPU.

I have tested the following beep patterns on Gigabyte, eVGA, and ECS motherboards. Other BIOS' may be different, but they all use a single short beep for a successful POST.

Breadboard - that will help isolate any kind of case problem you might have.
http://www.tomshardware.com/forum/262730-31-breadboardi...

Breadboard with just motherboard, CPU & HSF, case speaker, and PSU.

Make sure you plug the CPU power cable in. The system will not boot without it.

I always breadboard a new build. It takes only a few minutes, and you know you are putting good parts in the case once you are finished.

You can turn on the PC by momentarily shorting the two pins that the case power switch goes to. You should hear a series of long, single beeps indicating memory problems. Silence indicates a problem with (in most likely order) the PSU, motherboard, or CPU. Remember, at this time, you do not have a graphics card installed so the load on your PSU will be reduced.

If no beeps:
Running fans and drives and motherboard LED's do not necessarily indicate a good PSU. In the absence of a single short beep, they also do not indicate that the system is booting.

At this point, you can sort of check the PSU. Try to borrow a known good PSU of around 550 - 600 watts. That will power just about any system with a single GPU. If you cannot do that, use a DMM to measure the voltages. Measure between the colored wires and either chassis ground or the black wires. Yellow wires should be 12 volts. Red wires: +5 volts, orange wires: +3.3 volts, blue wire : -12 volts, violet wire: 5 volts always on. Tolerances are +/- 5% except for the -12 volts which is +/- 10%.

The gray wire is really important. It should go from 0 to +5 volts when you turn the PSU on with the case switch. CPU needs this signal to boot.

You can turn on the PSU by completely disconnecting the PSU and using a paperclip or jumper wire to short the green wire to one of the neighboring black wires.
http://www.youtube.com/watch?v=5FWXgQSokF4&feature=yout...

A way that might be easier is to use the main power plug. Working from the back of the plug where the wires come out, use a bare paperclip to short between the green wire and one of the neighboring black wires. That will do the same thing with an installed PSU. It is also an easy way to bypass a questionable case power switch.

This checks the PSU under no load conditions, so it is not completely reliable. But if it can not pass this, it is dead. Then repeat the checks with the PSU plugged into the computer to put a load on the PSU.

If the system beeps:
If it looks like the PSU is good, install a memory stick. Boot. Beep pattern should change to one long and several short beeps indicating a missing graphics card.

Silence, long single beeps, or series of short beeps indicate a problem with the memory. If you get short beeps verify that the memory is in the appropriate motherboard slots.

Insert the video card and connect any necessary PCIe power connectors. Boot. At this point, the system should POST successfully (a single short beep). Notice that you do not need keyboard, mouse, monitor, or drives to successfully POST.
At this point, if the system doesn't work, it's either the video card or an inadequate PSU. Or rarely - the motherboard's PCIe interface.

Now start connecting the rest of the devices starting with the monitor, then keyboard and mouse, then the rest of the devices, testing after each step. It's possible that you can pass the POST with a defective video card. The POST routines can only check the video interface. It cannot check the internal parts of the video card.
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April 16, 2011 4:29:42 PM

I'd pull the motherboard out and put it on a block of wood or cardboard. If I were a betting man, I'd wager there's a short.
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April 16, 2011 4:43:48 PM

I measured the voltage on each pin of the 24 pin connector, with and without load.
The load was the breadboard configuration of PSU, CPU, HSF. Connected to the MOBO was 24 pin, 4 pin CPU, CPU fan, and speaker.
The no load was PSU only with paperclip between green and black and a single fan connected.
All measurements were within tolerance.


Read the list like this:
Color = <load voltage> (<no load voltage>)

Orange = 3.31V (3.35V)
Blue = 22.58V (-11.89V)
Black
Green = -.06V (0V)
Black
Black
Black
Empty
Red = 4.9V (5.03V)
Red = 4.9V (5.03V)
Red = 4.9V (5.03V)
Black



Orange = 3.3V (3.33V)
Orange = 3.3V (3.33V)
Black
Red = 4.9V (5.02V)
Black
Red 4.98V (5.02V)
Black
Grey = 4.98V (5.03V)
Violet = 5V (5.03V)
Yellow = 12.06V (12V)
Yellow = 12.06V (12V)
Orange = 3.31V (3.33V)
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April 16, 2011 4:49:59 PM

Genny said:
I'd pull the motherboard out and put it on a block of wood or cardboard. If I were a betting man, I'd wager there's a short.



I've done that. I've got it sitting on a peice of statico foam. I also have a wrist strap connected to the chassis.
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April 18, 2011 4:57:19 AM

When I removed the HSF the CPU was fused to it. I was able to twist off the CPU. I reset the CPU in the socket. Plugged in the fan and just set it on CPU (no compound or clamping). Guess what …. I got Beeps!!!!! And the Dram LED came on. Oh! There was much rejoicing and jubilation. I decided to press my luck and inserted the RAM... Different beep pattern and the DRAM LED now went off. Yea! Passed the RAM check. I got brave and inserted the video card... And then a single beep!!! POST passed!!! Yippee!!! And then more beeps?! What?! Rejoicing and jubilation has now stopped. There can’t be any beeps after POST passed …can there?

So power on:
Beep
3-4 second pause
Fast beep-beep

After plugging in the monitor I noticed that the fast beeps corresponded to the first display on the monitor. Plugged in the keyboard and it is now:
Beep
3-4 second pause
Single beep

I can get into BIOS configuration.

So I believe that POST passed?? I am a bit confused by the pause and second beep. Is that to be expected?

Am I back to the point where I can put the MOBO back into the chassis? (after I clean an reapply thermal compound)
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April 18, 2011 5:53:34 AM

Either video adapter is bad or is not seated properly. Also, check to ensure the monitor cable is connected properly.
1 long, 2 short is adapter
1 long, 3 short is no adapter

odd that it didn't give you 1,3 if there was no adapter inserted
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February 10, 2012 7:53:24 AM

I have an ancient machine running on Win98 (because I have soundblaster gold that won't work with other OS). First I noticed that sometimes I needed to push power button more than once to power on (maybe that's irrelevant to the problem). Also, date and time would reset every time I power on (maybe that's irrelevant too). Then I started to have problem of having no beep when switching on (fan is working but system doesn't boot). Maybe it's my imagination, but when I switch it on, it's like I hear some tiny attempt to beep, some very weak, short sound of that kind. So I have to switch it off and one repeatedly, sometimes 30 or 40 times until I get lucky and it finally beeps, but as time passes by, I have impression that odds that it will beep are smaller and smaller (it still can beep but after many attempts). I removed the RAM module, cleaned it and put it back and it started to produce long, endlessly repeating beeps. I checked and saw that the RAM was not properly inserted so I fixed and it miraculously worked. I thought I'd solved the problem, but tomorrow again no beep. Changing RAM slots or removing and cleaning graphic card didn't work. I didn't touch the battery but I did do that thing with the jumper on MoBo for about 2 minutes or so. Didn't work.
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June 17, 2014 1:44:15 PM

pjmelect said:
Bad news for you, not having the battery in does not stop the computer from booting. I would start the RMA procedure or bet yet figure out what you have done wrong.


Apologies for reviving an old post, but I couldn't resist saying that bad battery or no battery CAN in certain cases prevent a mobo from POSTing. I am testing 200-250 mobos a year and this is entirely based on my own experience.

Regards.
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