|People frequently assume there's a problem with the mboard, or the processor, when the computer won't boot normally.|
It's a lot more likely something else was wrong.
What were your symptoms before you replaced the mboard?
A cmos battery that is too weak or dead cannot cause a computer there is nothing else wrong with to not boot normally or not boot at all.
A cmos battery usually lasts at least 5 years before it is too weak or is dead. If the mboard is newer than that there's probably nothing wrong with the cmos battery. You can check it's voltage with a volt meter in any case - the voltage it's supposed to have is stamped or printed on it.
If the cmos battery is too weak or dead, or if it's installed backwards, or if it has a poor connection to it's socket contacts, or if it's not installed, or if it's installed properly and it's okay and you moved a jumper on the mboard to clear the cmos then moved it back, if nothing else is wrong, you get a "Cmos Checksum Error" or similar message when you boot the computer. If there's nothing wrong with the battery or the way it's installed or it's connection, if you go into the bios Setup and set at least the date and time, save settings, you won't get that message while booting after that.
Failing power supplies are common and can cause your symptoms.
Check your PS.
They often partially work, fans and hard drives may spin, leds may come on, yet you may get no video and the mboard will not boot all the way.
See response 4 in this:
If it is failing, you can usually replace it with any decent standard sized standard ATX PS with the same capacity or greater.
Standard (PS/2) power supply size - 86mm high, 150mm wide, 140mm deep, or 3 3/8" h x 5 7/8" w x 5 1/2" d , or very close to that, though the depth can be more or less for some PSs.
Don't buy an el-cheapo PS.
See response 3 in this:
Your power supply must have at least the minimum capacity required to support a system with the graphics card you are using installed, or the max graphics card you might install in the future.
(Onboard video - video built into the mboard - IS NOT A CARD!)
You can go to the video card maker's web site and look up the specs for the model - often under system requirements - the minimum PS wattage, and, more important, the minimum amperage the PS must supply at 12v is stated. If you don't find that, any card with the same video chipset including any letters after the model number has very similar minimum PS requirements.
Some power supplies have more than one +12v amperage rating - in that case you add the rated max amperages to determine the total +12v amperage rating.
Some HP desktop models have a BESTEC power supply.
El-cheapo PSs tend to fail more often than average, and when the power supply fails completely, they are a lot more likely than average to damage something else, often the mboard.
This is especially the case if it's a BESTEC power supply!!
Unplug the cord to the computer, or otherwise switch off the AC power to it, open up the computer case, and find the label on the power supply - if the brand is BESTEC I advise you, if you find ANY indication the power supply might be in the process of failing, DO NOT trying booting the computer anymore - if the PS fails completely there is a strong likelyhood it will trash your mboard!!!!
If you HAVE NOT changed which ram you have installed in the mboard since it last worked properly, or in any case:
A common thing that can happen with ram, even ram that worked fine previously, is the ram has, or has developed, a poor connection in it's slot(s).
This usually happens a long time after the ram was installed, but it can happen with new ram, or after moving the computer case from one place to another, and I've had even new modules that needed to have their contacts cleaned.
See response 2 in this - try cleaning the contacts on the ram modules, and making sure the modules are properly seated:
If you HAVE changed which ram you have installed in the mboard since it last worked properly.....
Ram that works in another mboard , or any ram you buy or have lying around, may not work properly, or sometimes, not at all - even if it physically fits and is the right overall type (e.g. SDram, DDR, DDR2, etc.; PCxxxx, xxx mhz) for your mboard. In the worst cases of incompatibilty your mboard WILL NOT BOOT all the way with it installed, and the mboard may not even beep - the ram has to be compatible with the mboard's main chipset, or in the case of recent mboards, compatible with the memory controller built into the cpu.
The same applies for testing your ram in another mboard - the ram must be compatible with the other mboard - if it isn't, any results of testing the ram on the other mboard cannot be relied upon to be valid.
If you still have the ram that was installed when the system worked fine, and you're sure which module(s) it is, try installing just that ram.
If you're not sure whther the ram you have installed is compatible....
It is easy to test for incompatible ram that has caused your mboard to fail to boot.
Make sure you have a speaker or speakers or the equivalent connected to the mboard so you can hear mboard beeps (see your mboard manual or owner's manual if you need to).
Remove the AC power to the case/power supply.
Remove all the ram.
Restore AC power.
Try to boot.
If nothing else is wrong, you will get no video but you will hear a pattern of beeps that indicate no ram is installed, or a ram problem.
E.g. for an Award bios or a bios based on one, that's often a beep of about a half second, silence for a half second, a beep of about a half second, silence for a half second, continuously.
You may have a iffy connection inside the case somwhere.
Unplug the case/power supply.
Power off your monitor.
Open up the case by removing the left panel as seen when you're looking at the front of the case.
Check all the connections of the wiring to make sure they are all the way onto their pins and into their sockets, especially the main connector from the power supply. The wires close to the mboard going into the main power connector/socket should be more or less perpendicular to the mboard surface rather than at an angle. Most mboards require an additional connector from the PS be connected to a socket for power on the mboard, other than the main socket. Make sure all cards in slots are all the way down in their slots.
While you're in there, if the cpu fan/heatsink has mung (dust, lint, etc.) on it, clean it off, but DO NOT use a vaccuum cleaner to do that (they produce a tremendous amount of static electricity when running, and anything connected to them can discharge that to your components) - use canned air, or an air nozzle if you have access to an air compressor, or an artist's brush that can be used in small spaces, etc. It may be difficult to clean the top of the heatsink under the cpu fan - the most likely place to have mung on it - and the bottom side of the cpu fan blades unless you remove the fan. If you have a case fan, clean that too if it needs it.
With the cover still off, restore the AC power, start the computer and make sure the cpu fan spins
- if it doesn't spin, if you're sure the power supply is working okay, don't use the computer until you have found out why it doesn't spin (see next below).
- If it spins too slowly, and/or if it makes rattling or screeching noises, most likely to be noticed when the computer has cooled to room temp, has not been used for a while, and then is started up, the cpu fan's bearings are failing - replace it as soon as you can.
There's usually nothing wrong with the processor - cpu - unless the cpu fan failed.
If the cpu fan does not spin,
- if it's blade moves easily when you try to spin it with your finger, there may be nothing wrong with it. Try removing it and connecting it to another desktop mboard's 3 pin header for a case or power supply fan - if it spins, your processor is probably okay - if it doesn't spin your processor MAY be burnt out.
- if the cpu fan is difficult or impossible to spin when you try to spin it with your finger, you processor is probably burnt out.
Pictures of blown capacitors, other components - power supplies, Athlon cpu's, etc.:
"If the processor was dead wouldn't it still boot to the bios? "
but usually it's something else that's wrong.