Glossary

APC - Asynchronous Procedure Calls. Similar to DPC.

DMA - Direct Memory Access

DPC - Deferred Procedure Call. Procedures execute in a "deferred" fashion, that is, when all ISRs associated with I/O events and IPIs have completed. DPCs allow ISRs to defer work till a later time, thus minimizing the amount of work done at elevated interrupt priority level in the ISR.

FP - Floating Point

I/O - Input and Output

IPI - Interprocessor Interrupt. An interrupt sent from one processor to one, several, or all others in the system. Interprocessor interrupts are used by host processors to send messages to each other. They have no particular relationship to I/O.

ISR - Interrupt Service Routine. The routine (procedure) executed when a processor receives an interrupt.

MP - Multi-Processor. Refers to a class of computer which has more than one main processor used to execute general system code and user application code. Is not intended to refer to computers that use additional processors to control I/O, etc.

NMI - Non-Maskable Interrupt. A class of interrupt which is not masked out by the usual interrupt control instructions. Must only be used for very special hardware failures. (See text under Interrupts).

OEM - Original Equipment Manufacturer

OS - Operating System.

Scatter/Gather - As applied to DMA, means a mechanism by which a DMA operation may read from/write to multiple discontiguous chunks of physical memory. Essential to good performance in a paged environment.