A machine check exception (MCE) is triggered when the central processing unit (CPU) of a computer identifies a computer hardware error during system checks. Linux and Unix-based systems, including Apple® Mac computers, will report the error via a "kernel panic" message, often displayed directly on the console screen. Personal computers running the one of the Microsoft Windows® operating systems will utilize the commonly known "blue screen of death" to display a stop message. A machine check exception will require a restart of the system and often acts to identify underlying hardware corruption or compatibility issues.
There are a variety of issues that can initiate a machine check exception. The exception will occur where a specific hardware problem cannot be fully identified; this can make pinpointing the source of the exception quite labor intensive. Computer hardware problems that can result in this type of problem include memory cache errors in which the information stored in the memory cache becomes corrupted, causing computer errors whenever it is read, and random access memory (RAM) corruption in which incorrectly stored data in the system RAM can result in random errors occurring.
On Unix-based systems, machine check exceptions are commonly caused by the installation of new hardware. The commencement of these exceptions can often be traced to the time of the hardware installation to identify the corrupted hardware. Corrupted RAM expansion modules can cause such exceptions at random times, which makes identifying the underlying problem more complicated. Corrupted or incorrectly specified RAM memory expansion modules can also result in a machine check exception occurring in computers running on Microsoft Windows® operating systems.
System overheating can cause machine check exceptions to occur; this can happen as a result of an underpowered or defective heat-sink or fan or through computer modification or over-clocking of the CPU to run at a faster speed than originally set. More rarely, software errors can result in this type of problem. This usually would result from writing corrupted data to a file system or through software instructions to read corrupted or incorrectly identified memory blocks.
A machine check exception message is often a result of hardware failure or system architecture corruption where the computer error cannot be more accurately identified. The machine check architecture (MCA) is the means by which computer errors are reported to the installed operating system. Computers running on certain processors might employ a more advanced machine check architecture that can identify more specifically the cause of the problem.