Machine-check exception

A machine check exception (MCE) is a type of computer error that occurs when a problem involving the computer's hardware is detected. With most mass-market personal computers, an MCE indicates faulty or misconfigured hardware. The nature and causes of MCEs can vary by architecture and generation of system. In some designs, an MCE is always an unrecoverable error, that halts the machine, requiring a reboot. In other architectures, some MCEs may be non-fatal, such as for single-bit errors corrected by ECC memory. On some architectures, such as PowerPC, certain software bugs can cause MCEs, such as an invalid memory access. On other architectures, such as x86, MCEs typically originate from hardware only. IBM System/360 Operating System (OS/360) records input/output errors in a dataset called SYS1.LOGREC. Since then IBM has coined the term error recording data set (ERDS) for successor versions that allow the installation to choose the name and for operating systems not derived from OS/360. In OS/360, the installation can choose several levels of support for handling machine checks. The most sophisticated, Machine Check Handler (MCH), records failure data on SYS1.LOGREC and attempts recovery. The installation can print those data using the Environmental Record Editing and Printing Program (EREP) service aid or the stand-alone version SEREP. The MCH can handle memory failures in refreshable nucleus control sections by reading a fresh copy from SYS1.ASRLIB and can handle memory errors in SVC transient areas by reading a fresh copy of the SVC module from SYS1.SVCLIB. In z/OS the installation can either use an ERDS or can define a z/OS System Logger log stream to hold the error data. As with OS/360, the installation uses EREP to print those data; SEREP is no longer available. The MCH is no longer optional, and handles many more failure modes than the OS/360 MCH. On Microsoft Windows platforms, in the event of an unrecoverable MCEs, the system generates a BugCheck — also called a STOP error, or a Blue Screen of Death.