Browse Prior Art Database

Method of Emulating Memory Mapped I/O Devices in a Virtual Memory Environment

IP.com Disclosure Number: IPCOM000099560D
Original Publication Date: 1990-Feb-01
Included in the Prior Art Database: 2005-Mar-15
Document File: 1 page(s) / 23K

Publishing Venue

IBM

Related People

Butler, ND: AUTHOR [+3]

Abstract

Described in this disclosure is an easy elegant method of emulating memory mapped input/output devices on new virtual memory (VM) systems, thus permitting use with I/O units physically absent.

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Method of Emulating Memory Mapped I/O Devices in a Virtual Memory Environment

       Described in this disclosure is an easy elegant method of
emulating memory mapped input/output devices on new virtual memory
(VM) systems, thus permitting use with I/O units physically absent.

      In a virtual memory environment a page or segment of
addressable memory may not be present in real memory.  If it is
accessed a page fault or a similar exception will be raised, causing
a processor interrupt.  This concept can easily be extended to memory
mapped input/ output devices. The memory area being emulated can be
made non-resident. Whenever a program accesses the emulated device
area an exception is raised, which will interrupt the processor,
allowing it to emulate the input/output device.

      This disclosure only applies to memory mapped devices.
Architectural restriction may exist between some I/O devices and a
particular VM system.