.
Your PC motherboard provides the main infrastructure of the computer, hosting the CPU, RAM and add-in adapters, and provide interfaces for all drives and peripherals. The motherboard, CPU and RAM troubleshooting flowchart below is one of 17 flowcharts from "Computer Repair with Diagnostic Flowcharts Revised Edition." If you find it useful, as tens of thousands of home hobbyists and techs in training have, you can instantly download the printable eBook version anywhere in the world, or order the printed book through any bookstore.
Does the PC start the boot process and get at least as far as displaying a message from the BIOS or any signs of life from Windows? If all you get is a text message telling you that the monitor can't detect a video signal, it doesn't count, since the monitor can display that message with no computer present.
Return to Diagnostic Chart
Do you see positive signs that the PC is powering up? If you can't tell, start with the flowchart for troubleshooting PC power problems. We don't need Windows to appear here, just proof that the PC is at least partially alive.
Return to Diagnostic Chart
If you haven't been there already, start with the flowchart for troubleshooting video failures. Before we start trying to work out whether the failure is with the motherboard, the CPU or the RAM, we have to eliminate all the obvious possibilities, like the power supply and the video adapter, that can prevent the motherboard from functioning or communicating with you through the monitor. That's why you should always go through the previous two flowcharts before you start worrying about the processor, memory, or mainboard.
Return to Diagnostic Chart
Of all the issues that can go wrong after you replace the motherboard or upgrade the memory, failure to install the memory modules properly is the most frequently encountered problem. Modern motherboards all use some form of DIMM (Dual Inline Memory Modules). The older single channel (one DIMM per bank) motherboards are pretty much gone now, but dual channel (two DIMMs per bank) and triple channel (three DIMMs per bank) are in wide usage. All DIMM sockets are equipped with a locking lever on either end, and these levers must be opened (lowered) before inserting the DIMM, and should rise up and snap closed of their own accord as it seats. For new builds or upgrades, check the motherboard manufacturer compatibility list for RAM manufacturers. Even though DIMM memory is designed to exacting standards, the timing signals are so fussy that memory not tested and approved for a particular motherboard will often fail.
If your PC is more than eight years old, you may have the obsolete RIMM (Rambus Inline Memory Module) memory which required CRIMMs (Continuity RIMMs) in empty slots. I don't remember the last time I saw a SIMM (Single Inline Memory Modules), but they were 16 bit, so 32 bit processors required matched pairs.
Return to Diagnostic Chart
The CPU version of faulty DIMM insertion is both harder to spot and harder to check. While memory modules can be popped in and out in a second, the massive heatsinks on today's high power processors are secured to the motherboard with strong spring clips that aren't designed for frequent operation. As the number of electrical contacts on CPU packages has soared above a thousand, CPU manufacturers have largely dropped putting the pins on the CPU in favor of putting the pins in the socket, the LGA (Land Grid Array) design. LGA CPU's are much more likely to sit flat and clamp down evenly than the older packages with pins or legs that could easily bind in the socket and hold one side of the CPU package out of contact while seemingly seated. In any case, you should always make sure your CPU sits dead flat in the socket before installing the heat sink.
Return to Diagnostic Chart
A dead CPU means nothing else is going to work until you replace it. Since all CPUs require an active heatsink with a fan, any time you see the fan isn't working with the system powered on, there's a good chance the CPU it was supposed to be cooling is dead or is shutting itself down soon after boot for thermal protection. If you're building your own PC make sure you hook the CPU fan up to the power point indicated by the motherboard manual, rather than any random fan power point, because the ability of the BIOS (and by extension the operating system) to monitor and control the CPU fan behavior depends on the power being hooked up to the designated point.
Return to Diagnostic Chart
If the system powers on, does it beep once or does it beep multiple times? One beep means it has passed it's self check and is continuing to try to boot, multiple beeps indicate a problem with hardware. Beep codes have been around for nearly 30 years now, and in the early days, they pointed out failures with the many discrete chips on the motherboard that could be replaced. These days, practically all of those functions are integrated in the motherboards non-replaceable chipset, so the only failures you can remedy are those relating to the CPU, RAM or the video adapter. You can look up the beep codes used by the BIOS supplier for your particular motherboard, but generally the longer strings are a video adapter problem and the shorter strings are RAM failure. Anytime you hear beep codes, it pays to reseat the DIMMs and the video adapter because it only takes a minute. Just makes sure there isn't something resting on the keyboard, which can produce an unending string of beeps.
Return to Diagnostic Chart
Are the default settings in CMOS Setup chosen for the motherboard? If you've built a new PC or if you've been playing with overclocking an existing CPU and motherboard combination, the best troubleshooting step at this point is to restore the defaults. New motherboards do this through CMOS but old motherboards often used motherboard jumpers or even DIP switch banks (albeit a long time ago). If CMOS Setup doesn't offer an option to restore the defaults, you'll have to inspect the motherboard (or the documentation) for jumpers.
Before you move to the next step, it make sense to try the bare bones configuration suggested in power supply troubleshooting. Strip out everything except the video adapter and disconnect all the drives to see if you can get as far as a live screen with a boot failure message stating that no operating system is found..
Return to Diagnostic Chart
Rebuilding the computer outside of the case is the last step in troubleshooting to eliminate mechanical binding due to installation in the case and to make sure there are no shorts under the motherboard. And if you're going to to swap the CPU, it's simply easier to do with the motherboard on the bench than buried in the case, particularly in small format ATX cases with the power supply right next to the CPU socket. You shouldn't try this procedure if you aren't comfortable working around live electronics, and you should never walk away from a system built up without a case or you may come back to find a fire.
If you've built the PC yourself in a custom case, make sure that you haven't accidentally included metal standoffs where the motherboard didn't offer a grounding point, and if you're using standoffs from your spare parts pile, make sure that they are all the same height. Whenever I build a PC, I count the number of standoffs installed, and lay aside that number of screws for securing the motherboard. If I don't use up all the screws, I know something is wrong, that there's a standoff in the wrong place with no screw hole in the motherboard. If the system boots up fine without the case and fails again as soon as you reinstall it, try another case and power supply.
Return to Diagnostic Chart
If the motherboard is new, whether a new build or replacement, it's time to get an RMA and send it back to the retailer. If it's an old motherboard, and running the system outside of the case still won't light up the screen, there's not much left to try other than a CPU swap. If you already noticed that the fan on the heatsink was dead, buying a new CPU (and a new heatsink) is a good gamble, but if the fan was operating, you have to ask yourself if you really want to own that generation of CPU if it turns out the motherboard is faulty and you now have to replace that as well. If the motherboard is old, you should be able to find a cheap CPU as a "pull", a CPU removed from a working PC by a scrap operation. Try eBay and Amazon Marketplace for sellers.
Return to Diagnostic Chart
Does the system beep once and then freeze before beginning to load Windows? Freeze up could occur at a splash screen from the Video adapter BIOS or from the motherboard BIOS, or on older systems, during the memory count or while verifying DMI data pool. Problems with multi-core CPU throttling or CPU parking (you can see these in newer Windows versions through the Task Manager > Performance tab) reduce performance but don't impact anything before the operating system starts to load. Some older Windows installations may fail on dual-core and quad-core CPUs unless you disable all but one core. Sometimes it will be obvious there's a problem managing the multi-core CPU when you look at the performance and see one or more cores pegged at 100% when they shouldn't be doing anything, but those aren't boot issues.
Return to Diagnostic Chart
Strip out all the add-in cards except the video and disconnect the drives and see if you can get passed the freeze. If the PC now tries to boot and gets as far as complaining about no operating system, reconnect the hard drive and proceed from there.
Return to Diagnostic Chart
The nice thing about single channel memory systems is you only need two DIMMs to troubleshoot whether one is bad by installing just one DIMM in bank zero, and then the other. Dual channel memory means you need to own four DIMMS to swap banks, though three DIMMs will allow you to shuffle two at a time through a dual channel set-up and may allow you to spot the bad memory module. But all three pieces need to be matched (same manufacturer) or they probably won't play together. The newest motherboard with triple channel RAM mean it takes a minimum of four matched DIMMs go through the possible combinations to eliminate one bad piece, or six DIMMs to swap them out in one shot.
It's a good time to double check that the RAM you are using was tested and approved by the motherboard manufacturer. Using unapproved RAM may be responsible for intermittent lock-ups, which are nearly impossible to diagnose unless they get worse over time or you take the initiative to swap out the RAM with approved DIMMs.
Return to Diagnostic Chart
If you've changed the CMOS settings from the factory default, try restoring them. This is usually a main menu item is CMOS Setup. If you've been overclocking and resetting to the default allows you to boot, don't rush to start overclocking again, give the system a day or two to see if it's stable now. Don't assume that overclocking has to work in your PC because you read on the Internet where somebody with the same motherboard, CPU and RAM got it to work. Overclocking is about pushing components beyond their rated capacity, so the guy who it worked for may have got pieces that are simply better than yours.
Return to Diagnostic Chart
An overheating CPU will either lock up the PC or lead to automatic shut-down for thermal protection. If you're getting unintended shut-downs, or if you monitor the CPU temperature from CMOS Setup or within the operating system and see that it's running too hot (and running away), the only thing to try is redoing the thermal compound or replacing the heatsink. With the system shut down and the power cord unplugged, remove the existing heatsink and check the condition of the existing thermal paste or pad. I've always used alcohol for cleaning electronics, other people have their own methods, the important thing is not to leave a foreign residue before you apply the new thermal paste.
Don't go over the top with thermal grease or you'll just make a mess. The grease isn't a gasket or a sealer, it's just there to fill in the microscopic pits and valleys in the CPU to bring them into thermal contact with the heatsink. And don't use some random goo you had lying around the house for thermal grease, buy some from an electronics store or online.
If the fan on your heatsink doesn't spin when it's powered, you may be able to replace just the fan (if you can find one that size) or you may have to purchase a new heatsink with the fan installed. Avoid buying a generic heatsink that's supposed to work with a lot of different systems. Try finding one designed for you particular motherboard socket and CPU by searching online stores that sell motherboard and CPU bundles, and checking what heatsink they provide with your particular motherboard and CPU.
PC Memory, Processor and Motherboard Diagnostic Flowchart
"Warning! You must unplug your ATX power supply from the wall before working inside the case.Your PC motherboard provides the main infrastructure of the computer, hosting the CPU, RAM and add-in adapters, and provide interfaces for all drives and peripherals. The motherboard, CPU and RAM troubleshooting flowchart below is one of 17 flowcharts from "Computer Repair with Diagnostic Flowcharts Revised Edition." If you find it useful, as tens of thousands of home hobbyists and techs in training have, you can instantly download the printable eBook version anywhere in the world, or order the printed book through any bookstore.
CPU, RAM and Motherboard Troubleshooting
Note that these steps correspond with decision points on the flowchart and are reached directly by clicking on the diamond symbols. The text below cannot be read sequentially.Does the PC start the boot process and get at least as far as displaying a message from the BIOS or any signs of life from Windows? If all you get is a text message telling you that the monitor can't detect a video signal, it doesn't count, since the monitor can display that message with no computer present.
Return to Diagnostic Chart
Do you see positive signs that the PC is powering up? If you can't tell, start with the flowchart for troubleshooting PC power problems. We don't need Windows to appear here, just proof that the PC is at least partially alive.
Return to Diagnostic Chart
If you haven't been there already, start with the flowchart for troubleshooting video failures. Before we start trying to work out whether the failure is with the motherboard, the CPU or the RAM, we have to eliminate all the obvious possibilities, like the power supply and the video adapter, that can prevent the motherboard from functioning or communicating with you through the monitor. That's why you should always go through the previous two flowcharts before you start worrying about the processor, memory, or mainboard.
Return to Diagnostic Chart
Of all the issues that can go wrong after you replace the motherboard or upgrade the memory, failure to install the memory modules properly is the most frequently encountered problem. Modern motherboards all use some form of DIMM (Dual Inline Memory Modules). The older single channel (one DIMM per bank) motherboards are pretty much gone now, but dual channel (two DIMMs per bank) and triple channel (three DIMMs per bank) are in wide usage. All DIMM sockets are equipped with a locking lever on either end, and these levers must be opened (lowered) before inserting the DIMM, and should rise up and snap closed of their own accord as it seats. For new builds or upgrades, check the motherboard manufacturer compatibility list for RAM manufacturers. Even though DIMM memory is designed to exacting standards, the timing signals are so fussy that memory not tested and approved for a particular motherboard will often fail.
If your PC is more than eight years old, you may have the obsolete RIMM (Rambus Inline Memory Module) memory which required CRIMMs (Continuity RIMMs) in empty slots. I don't remember the last time I saw a SIMM (Single Inline Memory Modules), but they were 16 bit, so 32 bit processors required matched pairs.
Return to Diagnostic Chart
The CPU version of faulty DIMM insertion is both harder to spot and harder to check. While memory modules can be popped in and out in a second, the massive heatsinks on today's high power processors are secured to the motherboard with strong spring clips that aren't designed for frequent operation. As the number of electrical contacts on CPU packages has soared above a thousand, CPU manufacturers have largely dropped putting the pins on the CPU in favor of putting the pins in the socket, the LGA (Land Grid Array) design. LGA CPU's are much more likely to sit flat and clamp down evenly than the older packages with pins or legs that could easily bind in the socket and hold one side of the CPU package out of contact while seemingly seated. In any case, you should always make sure your CPU sits dead flat in the socket before installing the heat sink.
Return to Diagnostic Chart
A dead CPU means nothing else is going to work until you replace it. Since all CPUs require an active heatsink with a fan, any time you see the fan isn't working with the system powered on, there's a good chance the CPU it was supposed to be cooling is dead or is shutting itself down soon after boot for thermal protection. If you're building your own PC make sure you hook the CPU fan up to the power point indicated by the motherboard manual, rather than any random fan power point, because the ability of the BIOS (and by extension the operating system) to monitor and control the CPU fan behavior depends on the power being hooked up to the designated point.
Return to Diagnostic Chart
If the system powers on, does it beep once or does it beep multiple times? One beep means it has passed it's self check and is continuing to try to boot, multiple beeps indicate a problem with hardware. Beep codes have been around for nearly 30 years now, and in the early days, they pointed out failures with the many discrete chips on the motherboard that could be replaced. These days, practically all of those functions are integrated in the motherboards non-replaceable chipset, so the only failures you can remedy are those relating to the CPU, RAM or the video adapter. You can look up the beep codes used by the BIOS supplier for your particular motherboard, but generally the longer strings are a video adapter problem and the shorter strings are RAM failure. Anytime you hear beep codes, it pays to reseat the DIMMs and the video adapter because it only takes a minute. Just makes sure there isn't something resting on the keyboard, which can produce an unending string of beeps.
Return to Diagnostic Chart
Are the default settings in CMOS Setup chosen for the motherboard? If you've built a new PC or if you've been playing with overclocking an existing CPU and motherboard combination, the best troubleshooting step at this point is to restore the defaults. New motherboards do this through CMOS but old motherboards often used motherboard jumpers or even DIP switch banks (albeit a long time ago). If CMOS Setup doesn't offer an option to restore the defaults, you'll have to inspect the motherboard (or the documentation) for jumpers.
Before you move to the next step, it make sense to try the bare bones configuration suggested in power supply troubleshooting. Strip out everything except the video adapter and disconnect all the drives to see if you can get as far as a live screen with a boot failure message stating that no operating system is found..
Return to Diagnostic Chart
Rebuilding the computer outside of the case is the last step in troubleshooting to eliminate mechanical binding due to installation in the case and to make sure there are no shorts under the motherboard. And if you're going to to swap the CPU, it's simply easier to do with the motherboard on the bench than buried in the case, particularly in small format ATX cases with the power supply right next to the CPU socket. You shouldn't try this procedure if you aren't comfortable working around live electronics, and you should never walk away from a system built up without a case or you may come back to find a fire.
If you've built the PC yourself in a custom case, make sure that you haven't accidentally included metal standoffs where the motherboard didn't offer a grounding point, and if you're using standoffs from your spare parts pile, make sure that they are all the same height. Whenever I build a PC, I count the number of standoffs installed, and lay aside that number of screws for securing the motherboard. If I don't use up all the screws, I know something is wrong, that there's a standoff in the wrong place with no screw hole in the motherboard. If the system boots up fine without the case and fails again as soon as you reinstall it, try another case and power supply.
Return to Diagnostic Chart
If the motherboard is new, whether a new build or replacement, it's time to get an RMA and send it back to the retailer. If it's an old motherboard, and running the system outside of the case still won't light up the screen, there's not much left to try other than a CPU swap. If you already noticed that the fan on the heatsink was dead, buying a new CPU (and a new heatsink) is a good gamble, but if the fan was operating, you have to ask yourself if you really want to own that generation of CPU if it turns out the motherboard is faulty and you now have to replace that as well. If the motherboard is old, you should be able to find a cheap CPU as a "pull", a CPU removed from a working PC by a scrap operation. Try eBay and Amazon Marketplace for sellers.
Return to Diagnostic Chart
Does the system beep once and then freeze before beginning to load Windows? Freeze up could occur at a splash screen from the Video adapter BIOS or from the motherboard BIOS, or on older systems, during the memory count or while verifying DMI data pool. Problems with multi-core CPU throttling or CPU parking (you can see these in newer Windows versions through the Task Manager > Performance tab) reduce performance but don't impact anything before the operating system starts to load. Some older Windows installations may fail on dual-core and quad-core CPUs unless you disable all but one core. Sometimes it will be obvious there's a problem managing the multi-core CPU when you look at the performance and see one or more cores pegged at 100% when they shouldn't be doing anything, but those aren't boot issues.
Return to Diagnostic Chart
Strip out all the add-in cards except the video and disconnect the drives and see if you can get passed the freeze. If the PC now tries to boot and gets as far as complaining about no operating system, reconnect the hard drive and proceed from there.
Return to Diagnostic Chart
The nice thing about single channel memory systems is you only need two DIMMs to troubleshoot whether one is bad by installing just one DIMM in bank zero, and then the other. Dual channel memory means you need to own four DIMMS to swap banks, though three DIMMs will allow you to shuffle two at a time through a dual channel set-up and may allow you to spot the bad memory module. But all three pieces need to be matched (same manufacturer) or they probably won't play together. The newest motherboard with triple channel RAM mean it takes a minimum of four matched DIMMs go through the possible combinations to eliminate one bad piece, or six DIMMs to swap them out in one shot.
It's a good time to double check that the RAM you are using was tested and approved by the motherboard manufacturer. Using unapproved RAM may be responsible for intermittent lock-ups, which are nearly impossible to diagnose unless they get worse over time or you take the initiative to swap out the RAM with approved DIMMs.
Return to Diagnostic Chart
If you've changed the CMOS settings from the factory default, try restoring them. This is usually a main menu item is CMOS Setup. If you've been overclocking and resetting to the default allows you to boot, don't rush to start overclocking again, give the system a day or two to see if it's stable now. Don't assume that overclocking has to work in your PC because you read on the Internet where somebody with the same motherboard, CPU and RAM got it to work. Overclocking is about pushing components beyond their rated capacity, so the guy who it worked for may have got pieces that are simply better than yours.
Return to Diagnostic Chart
An overheating CPU will either lock up the PC or lead to automatic shut-down for thermal protection. If you're getting unintended shut-downs, or if you monitor the CPU temperature from CMOS Setup or within the operating system and see that it's running too hot (and running away), the only thing to try is redoing the thermal compound or replacing the heatsink. With the system shut down and the power cord unplugged, remove the existing heatsink and check the condition of the existing thermal paste or pad. I've always used alcohol for cleaning electronics, other people have their own methods, the important thing is not to leave a foreign residue before you apply the new thermal paste.
Don't go over the top with thermal grease or you'll just make a mess. The grease isn't a gasket or a sealer, it's just there to fill in the microscopic pits and valleys in the CPU to bring them into thermal contact with the heatsink. And don't use some random goo you had lying around the house for thermal grease, buy some from an electronics store or online.
If the fan on your heatsink doesn't spin when it's powered, you may be able to replace just the fan (if you can find one that size) or you may have to purchase a new heatsink with the fan installed. Avoid buying a generic heatsink that's supposed to work with a lot of different systems. Try finding one designed for you particular motherboard socket and CPU by searching online stores that sell motherboard and CPU bundles, and checking what heatsink they provide with your particular motherboard and CPU.
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