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Part of a series on
Microprocessor modes for the x86 architecture
Real mode (Intel 8086)
8080 emulation mode (NEC V20/V30 only)
Protected mode (Intel 80286)
Unreal mode (Intel 80286)
Virtual 8086 mode (Intel 80386)
System Management Mode (Intel 386SL)
Long mode (AMD Athlon 64)
x86 virtualization (Intel Pentium 4, AMD Athlon 64)
AIS mode (VIA C3 only)
First supported platform shown in parentheses
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System Management Mode (SMM, sometimes called ring −2 in reference to protection rings)[1][2] is an operating mode of x86 central processor units (CPUs) in which all normal execution, including the operating system, is suspended. An alternate software system which usually resides in the computer's firmware, or a hardware-assisted debugger, is then executed with high privileges.
It was first released with the Intel 386SL.[3][4] While initially special SL versions were required for SMM, Intel incorporated SMM in its mainline 486 and Pentium processors in 1993. AMD implemented Intel's SMM with the Am386 processors in 1991.[5] It is available in all later microprocessors in the x86 architecture.[citation needed]
In ARM architecture the Exception Level 3 (EL3) mode is also referred as Secure Monitor Mode or System Management Mode.[6]
^Domas, Christopher (2015-07-20). "The Memory Sinkhole" (PDF). Black Hat. Retrieved 2015-08-22.
^Tereshkin, Alexander; Wojtczuk, Rafal (2009-07-29). "Introducing Ring -3 Rootkits" (PDF). Invisible Things Lab, Black Hat USA. p. 4. Retrieved 2015-08-22.
^"SMIs Are EEEEVIL (Part 1)". msdn.com. Microsoft. 2020-07-17.
^Ellis, Simson C., "The 386 SL Microprocessor in Notebook PCs", Intel Corporation, Microcomputer Solutions, March/April 1991, page 20
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