Trap is known as Non-Maskable interrupts, which is used in emergency condition.

SIM is Set Interrupt Mask. Used to mask the hardware interrupts. RIM is Read Interrupt Mask. Used to check whether the interrupt is Masked or not.

An interrupt that can be turned off by the programmer is known as Maskable interrupt.

When a parity error occurs, a Non-Maskable Interrupt (NMI) signal is co-generated in the system, causing the BIOS to execute its NMI handler routine. This routine will normally place a parity error message onscreen, along with an option to shut down the system or to continue. In other cases, the system will show a short memory count during the POST and lock up without an error message. Another possibility is that the system will count the memory, lock up, and reboot itself. If the memory error occurs higher in the physical memory device, this situation can occur after the operating system and applications have been loaded and started running.

Missing expansion-slot covers adversely affect the system in two ways. First, the missing cover permits dust to accumulate in the system, forming an insulating blanket that traps heat next to active devices and causes them to overheat. Second, the heat problem is complicated further by the fact that the missing slot cover interrupts the designed airflow patterns inside the case, causing components to overheat because of missing or inadequate airflow.