Real mode - Revision history

Jnc: punc

2023-01-19T14:57:02Z

punc

← Older revision		Revision as of 14:57, 19 January 2023
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	==History==		==History==

	The first Intel 16/8 bit [[microprocessor]]s could only address 1Mb of physical [[main memory]]; later, Intel referred to these processors as real mode only. LIM memory was developed to [[swapping\|swap]] pages over the bus into the 1Mb [[address space]]. The Intel 8088, and 8086, had a real mode memory of 1Mb; since 384K was reserved for I/O pages, it created a real mode barrier of 640Kb of memory.		The first Intel 16/8 bit [[microprocessor]]s could only address 1Mb of physical [[main memory]]; later, Intel referred to these processors as 'real mode only'. LIM memory was developed to [[swapping\|swap]] pages over the bus into the 1Mb [[address space]]. The Intel 8088, and 8086, had a real mode memory of 1Mb; since 384K was reserved for I/O pages, it created a real mode barrier of 640Kb of memory.

	Later chips had developing memory modes: the Intel 80286 had a real mode address space of 1Mb, and a protected mode of 16Mb; these memory addresses could not only be relocated, but they could be swapped out to [[disk]]. (Virtual memory). Switching to protected mode was relativity simple, but switching back to real mode, required a processor reset.		Later chips had developing memory modes: the Intel 80286 had a real mode address space of 1Mb, and a protected mode of 16Mb; these memory addresses could not only be relocated, but they could be swapped out to [[disk]]. (Virtual memory). Switching to protected mode was relativity simple, but switching back to real mode required a processor reset.

	In Real mode, everything is 16 bits. The entire memory is not accessed with an absolute index from 0, but it is divided into segments. Each segment represents the actual offset from 0, multiplied by 16. To this segment, an offset value can be added to refer to a distance from the start of this segment.		In Real mode, everything is 16 bits. The entire memory is not accessed with an absolute index from 0, but it is divided into segments. Each segment represents the actual offset from 0, multiplied by 16. To this segment, an offset value can be added to refer to a distance from the start of this segment.

Jnc: +See also

2021-03-02T22:13:46Z

+See also

← Older revision		Revision as of 22:13, 2 March 2021
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	* Intel 80286 was a 16-bit processor with a 24-bit bus.		* Intel 80286 was a 16-bit processor with a 24-bit bus.
	* Intel 80836 was a 32-bit processor with a 32-bit bus, and a 16-bit real mode.		* Intel 80836 was a 32-bit processor with a 32-bit bus, and a 16-bit real mode.

			==See also==

			* [[Triple fault]]

	==External links==		==External links==

Jnc: better word

2021-03-02T22:01:22Z

better word

← Older revision		Revision as of 22:01, 2 March 2021
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	'''Real mode''' is an [[Intel]]-specific term used with the [[Intel 80286\|80286]] and later members of the [[Intel x86]] line which refers to a mode of the [[Central Processing Unit\|CPU]] in which the extended [[architecture]]s of the later chips, including hardware support for [[virtual memory]], is apparently (to the program) ''not'' ~~enabled~~.		'''Real mode''' is an [[Intel]]-specific term used with the [[Intel 80286\|80286]] and later members of the [[Intel x86]] line which refers to a mode of the [[Central Processing Unit\|CPU]] in which the extended [[architecture]]s of the later chips, including hardware support for [[virtual memory]], is apparently (to the program) ''not'' present.

	These [[integrated circuit\|chips]] power on in real mode, in which they appear to be [[Intel 8086\|8086]]'s; this is for purposes of [[backward compatibility]] at the [[object code]] level. A small extension to that architecture allows them to switch into [[protected mode]], where all the extended features of the later architectures are available. Real mode in the later x86 machines is almost entirely the same as an 8086, but there are minor differences (e.g. different Instruction Clock Counts).		These [[integrated circuit\|chips]] power on in real mode, in which they appear to be [[Intel 8086\|8086]]'s; this is for purposes of [[backward compatibility]] at the [[object code]] level. A small extension to that architecture allows them to switch into [[protected mode]], where all the extended features of the later architectures are available. Real mode in the later x86 machines is almost entirely the same as an 8086, but there are minor differences (e.g. different Instruction Clock Counts).

Jnc: start clean-up

2021-03-02T15:31:13Z

start clean-up

← Older revision		Revision as of 15:31, 2 March 2021
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	'''Real mode''' is ~~a processor memory addressing status where a pointer points~~ to a ~~exact place~~ in ~~memory with out redirection~~, ~~either through Virutal~~ memory, ~~Task virtualization, or relocateable task execution~~.		'''Real mode''' is an [[Intel]]-specific term used with the [[Intel 80286\|80286]] and later members of the [[Intel x86]] line which refers to a mode of the [[Central Processing Unit\|CPU]] in which the extended [[architecture]]s of the later chips, including hardware support for [[virtual memory]], is apparently (to the program) ''not'' enabled.

	'~~''Real Mode''' was coined~~ for the ~~ability of processors~~ to ~~change~~ where ~~a program assumed a memory address was,~~		These [[integrated circuit\|chips]] power on in real mode, in which they appear to be [[Intel 8086\|8086]]'s; this is for purposes of [[backward compatibility]] at the [[object code]] level. A small extension to that architecture allows them to switch into [[protected mode]], where all the extended features of the later architectures are available. Real mode in the later x86 machines is almost entirely the same as an 8086, but there are minor differences (e.g. different Instruction Clock Counts).
	~~so that it could be either relocated able~~, ~~or virtualized and moved~~.

	On Intel Processors, the first 16/8 bit microprocessors could only address 1Mb of memory, and later Intel reffered to these processors as real mode only. LIM memory was developed to swap pages over the bus into the 1Mb address space. The Intel 8088, and 8086, had a real mode memory of 1Mb, ( 16-bit addresses ). Since 384K was reserved for I/O pages, it created a real mode barrier of 640Kb of memory.		==History==

	~~These~~ [[~~integrated circuit\|chips~~]] ~~power on in real mode, in which they appear to be~~ [[~~Intel 8086\|8086~~]]'s; ~~this is for purposes of~~ [[~~backward compatibility~~]] at the [[~~object code~~]] ~~level~~. ~~A small extension to that architecture allows them to switch into [[protected~~ mode]], ~~where all the extended features~~ of ~~the later architectures are available. Real mode in the later x86 machines is almost entirely the same as the 8086, but there are minor differences (e.g. different Instruction Clock Counts)~~.		The first Intel 16/8 bit [[microprocessor]]s could only address 1Mb of physical [[main memory]]; later, Intel referred to these processors as real mode only. LIM memory was developed to [[swapping\|swap]] pages over the bus into the 1Mb [[address space]]. The Intel 8088, and 8086, had a real mode memory of 1Mb; since 384K was reserved for I/O pages, it created a real mode barrier of 640Kb of memory.

	~~Beginning with the [[Intel 80286\|80286]] and later members of the [[Intel x86]] line, refers to a mode of the [[Central Processing Unit\|CPU]] in which the extended [[architecture]]s of the later~~ chips~~, including hardware support for [[virtual memory]], is ''not'' enabled. So the architectures~~ had developing memory modes: ~~The~~ Intel 80286, had a real mode of 1Mb and a protected mode of 16Mb~~, which~~ memory ~~address~~ could not only be relocated, but they could be swapped out to disk. (Virtual memory). Switching to protected mode was relativity simple, but switching back to real mode, required a processor reset.		Later chips had developing memory modes: the Intel 80286 had a real mode address space of 1Mb, and a protected mode of 16Mb; these memory addresses could not only be relocated, but they could be swapped out to [[disk]]. (Virtual memory). Switching to protected mode was relativity simple, but switching back to real mode, required a processor reset.

	In Real mode, everything is 16 bits. The entire memory is not accessed with an absolute index from 0, but it is divided into segments. Each segment represents the actual offset from 0, multiplied by 16. To this segment, an offset value can be added to refer to a distance from the start of this segment.		In Real mode, everything is 16 bits. The entire memory is not accessed with an absolute index from 0, but it is divided into segments. Each segment represents the actual offset from 0, multiplied by 16. To this segment, an offset value can be added to refer to a distance from the start of this segment.

	The Intel 80386, had a real mode of 16Mb, and both a protected mode of 16Mb, which memory address could not only be relocated, but also could be swapped out to disk. The Intel 80386, also had a virtual 8086 mode, where memory address could not only be moved ( relocated ), and swapped to disk (virtualized), but with the ability to swap in register files (a complete set of 8086 registers ), could support a virtual machine environment. A task will run in real mode, unless virtual memory is on, and it is started in virtual 8086 mode.		The Intel 80386, had a real mode of 16Mb, and both a protected mode of 16Mb, which memory address could not only be relocated, but also could be swapped out to disk. The Intel 80386 also had a virtual 8086 mode, where memory address could not only be moved (relocated), and swapped to disk (virtualized), but with the ability to swap in [[register]] files (a complete set of 8086 registers), could support a virtual machine environment. A [[task]] will run in real mode, unless virtual memory is on, and it is started in virtual 8086 mode.

	Starting with the Westmere Processor core, not only were memory addresses virtualized, (VT-x) and register files virtualised, but I/O address could be virtualized (VT-d) which is direct I/O. A virtual machine can address Input/Output directly. In the x86-64 computer architecture, long mode is the mode where a 64-bit operating system can access 64-bit instructions and registers. ... Real mode or virtual 8086 mode programs cannot be natively run in long mode.		Starting with the Westmere Processor core, not only were memory addresses virtualized, (VT-x) and register files virtualised, but I/O address could be virtualized (VT-d) which is direct I/O. A virtual machine can address Input/Output directly. In the x86-64 computer architecture, long mode is the mode where a 64-bit operating system can access 64-bit instructions and registers. ... Real mode or virtual 8086 mode programs cannot be natively run in long mode.

	Intel 8088 was a 16-bit processor with an 8 bit bus.		* Intel 8088 was a 16-bit processor with an 8 bit bus.
	Intel 8086 was a 16-bit processor with a 16-bit bus.		* Intel 8086 was a 16-bit processor with a 16-bit bus.
	Intel 80286 was a 16-bit processor with a 24-bit bus.		* Intel 80286 was a 16-bit processor with a 24-bit bus.
	Intel 80836 was a 32-bit processor with a 32-bit bus, and a 16-bit real mode.		* Intel 80836 was a 32-bit processor with a 32-bit bus, and a 16-bit real mode.

	[https://www.codeproject.com/Articles/45788/The-Real-Protected-Long-mode-assembly-tutorial-for Real mode from a programming standpoint]		==External links==

			* [https://www.codeproject.com/Articles/45788/The-Real-Protected-Long-mode-assembly-tutorial-for Real mode from a programming standpoint]

	{{semi-stub}}		{{semi-stub}}

	[[Category: Intel Microprocessors]]		[[Category: Intel Microprocessors]]

ForOldHack: /* added link */

2020-07-02T01:31:42Z

added link

← Older revision		Revision as of 01:31, 2 July 2020
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	Intel 80286 was a 16-bit processor with a 24-bit bus.		Intel 80286 was a 16-bit processor with a 24-bit bus.
	Intel 80836 was a 32-bit processor with a 32-bit bus, and a 16-bit real mode.		Intel 80836 was a 32-bit processor with a 32-bit bus, and a 16-bit real mode.

			[https://www.codeproject.com/Articles/45788/The-Real-Protected-Long-mode-assembly-tutorial-for Real mode from a programming standpoint]

	{{semi-stub}}		{{semi-stub}}

	[[Category: Intel Microprocessors]]		[[Category: Intel Microprocessors]]

ForOldHack: /* redecorated */ Rearranged into paragraphs. ...

2020-07-02T01:29:38Z

redecorated: Rearranged into paragraphs. ...

← Older revision		Revision as of 01:29, 2 July 2020
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	so that it could be either relocated able, or virtualized and moved.		so that it could be either relocated able, or virtualized and moved.

	on Intel Processors, the first 16/8 bit microprocessors could only address 1Mb of memory, and later Intel reffered to these processors as real mode only. LIM memory was developed to swap pages over the bus into the 1Mb address space.		On Intel Processors, the first 16/8 bit microprocessors could only address 1Mb of memory, and later Intel reffered to these processors as real mode only. LIM memory was developed to swap pages over the bus into the 1Mb address space. The Intel 8088, and 8086, had a real mode memory of 1Mb, ( 16-bit addresses ). Since 384K was reserved for I/O pages, it created a real mode barrier of 640Kb of memory.

	~~Beginning with the~~ [[~~Intel 80286~~\|~~80286~~]] ~~and later members of the~~ [[Intel ~~x86~~]] ~~line, refers to a mode~~ of ~~the~~ [[~~Central Processing Unit\|CPU~~]] ~~in which~~ the ~~extended~~ [[~~architecture~~]]~~s of the later chips, including hardware support for~~ [[~~virtual memory~~]], is ~~''not'' enabled~~. ~~So the archictecutures had developing memory modes:~~		These [[integrated circuit\|chips]] power on in real mode, in which they appear to be [[Intel 8086\|8086]]'s; this is for purposes of [[backward compatibility]] at the [[object code]] level. A small extension to that architecture allows them to switch into [[protected mode]], where all the extended features of the later architectures are available. Real mode in the later x86 machines is almost entirely the same as the 8086, but there are minor differences (e.g. different Instruction Clock Counts).

	The Intel ~~8088, and 8086~~, had a real mode ~~memory~~ of 1Mb, ( ~~16-bit addresses~~ ). ~~Since 384K~~ was ~~reserved for I/O pages~~, ~~it created a~~ real mode ~~barrier of 640Kb of memory~~.		Beginning with the [[Intel 80286\|80286]] and later members of the [[Intel x86]] line, refers to a mode of the [[Central Processing Unit\|CPU]] in which the extended [[architecture]]s of the later chips, including hardware support for [[virtual memory]], is ''not'' enabled. So the architectures had developing memory modes: The Intel 80286, had a real mode of 1Mb and a protected mode of 16Mb, which memory address could not only be relocated, but they could be swapped out to disk. (Virtual memory). Switching to protected mode was relativity simple, but switching back to real mode, required a processor reset.

	~~The Intel 80286, had a real~~ mode ~~of 1Mb and a protected mode of 16Mb~~, ~~which~~ memory ~~address could~~ not ~~only be relocated~~, but ~~they could be swapped out to disk~~. ~~( Virtual memory )~~. ~~Switching~~ to ~~protected mode was relativity simple, but switching back~~ to ~~real mode, required~~ a ~~processor reset~~.		In Real mode, everything is 16 bits. The entire memory is not accessed with an absolute index from 0, but it is divided into segments. Each segment represents the actual offset from 0, multiplied by 16. To this segment, an offset value can be added to refer to a distance from the start of this segment.

	The Intel 80386, had a real mode of 16Mb, and both a protected mode of 16Mb, which memory address could not only be relocated, but also could be swapped out to disk.		The Intel 80386, had a real mode of 16Mb, and both a protected mode of 16Mb, which memory address could not only be relocated, but also could be swapped out to disk. The Intel 80386, also had a virtual 8086 mode, where memory address could not only be moved ( relocated ), and swapped to disk (virtualized), but with the ability to swap in register files (a complete set of 8086 registers ), could support a virtual machine environment. A task will run in real mode, unless virtual memory is on, and it is started in virtual 8086 mode.

	~~The Intel 80386~~, ~~also had a virtual 8086 mode, where memory address could~~ not only ~~be moved~~ ( ~~relocated~~ ), ~~and swapped to disk~~ ( ~~virtualized~~ ), ~~but with~~ the ~~ability to swap in register files (~~ a ~~complete set of 8086~~ registers ~~), could support a~~ virtual ~~machine environment~~.		Starting with the Westmere Processor core, not only were memory addresses virtualized, (VT-x) and register files virtualised, but I/O address could be virtualized (VT-d) which is direct I/O. A virtual machine can address Input/Output directly. In the x86-64 computer architecture, long mode is the mode where a 64-bit operating system can access 64-bit instructions and registers. ... Real mode or virtual 8086 mode programs cannot be natively run in long mode.

	~~Starting~~ with ~~the Westmere Processor core, not only were memory addresses virtualized, (VT~~-~~x) and register files virtualised, but I/O address could be virtualized (VT~~-~~d) which is direct I/O~~. ~~A virtual machine can address Input/Output directly~~.		Intel 8088 was a 16-bit processor with an 8 bit bus.
			Intel 8086 was a 16-bit processor with a 16-bit bus.
	~~These [[integrated circuit\|chips]] power on in real mode, in which they appear to be [[~~Intel ~~8086\|8086]]'s; this is for purposes of [[backward compatibility]] at the [[object code]] level. A small extension to that architecture allows them to switch into [[protected mode]]~~, ~~where all the extended features of the later architectures are available.~~		Intel 80286 was a 16-bit processor with a 24-bit bus.
			Intel 80836 was a 32-bit processor with a 32-bit bus, and a 16-bit real mode.
	~~Real~~ mode ~~in the later x86 machines is almost entirely the same as the 8086, but there are minor differences (e.g. different Instruction Clock Counts)~~.

	{{semi-stub}}		{{semi-stub}}

	[[Category: Intel Microprocessors]]		[[Category: Intel Microprocessors]]

ForOldHack: /* explain real mode for intel processors */ Can we get an explaination of real vs virtual memory for the VAX archicture?

2020-07-02T01:00:40Z

explain real mode for intel processors: Can we get an explaination of real vs virtual memory for the VAX archicture?

← Older revision		Revision as of 01:00, 2 July 2020
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	'''Real mode''', on the [[Intel 80286\|80286]] and later members of the [[Intel x86]] line, refers to a mode of the [[Central Processing Unit\|CPU]] in which the extended [[architecture]]s of the later chips, including hardware support for [[virtual memory]], is ''not'' enabled.		'''Real mode''' is a processor memory addressing status where a pointer points to a exact place in memory with out redirection, either through Virutal memory, Task virtualization, or relocateable task execution.

			'''Real Mode''' was coined for the ability of processors to change where a program assumed a memory address was,
			so that it could be either relocated able, or virtualized and moved.

			on Intel Processors, the first 16/8 bit microprocessors could only address 1Mb of memory, and later Intel reffered to these processors as real mode only. LIM memory was developed to swap pages over the bus into the 1Mb address space.

			Beginning with the [[Intel 80286\|80286]] and later members of the [[Intel x86]] line, refers to a mode of the [[Central Processing Unit\|CPU]] in which the extended [[architecture]]s of the later chips, including hardware support for [[virtual memory]], is ''not'' enabled. So the archictecutures had developing memory modes:

			The Intel 8088, and 8086, had a real mode memory of 1Mb, ( 16-bit addresses ). Since 384K was reserved for I/O pages, it created a real mode barrier of 640Kb of memory.

			The Intel 80286, had a real mode of 1Mb and a protected mode of 16Mb, which memory address could not only be relocated, but they could be swapped out to disk. ( Virtual memory ). Switching to protected mode was relativity simple, but switching back to real mode, required a processor reset.

			The Intel 80386, had a real mode of 16Mb, and both a protected mode of 16Mb, which memory address could not only be relocated, but also could be swapped out to disk.

			The Intel 80386, also had a virtual 8086 mode, where memory address could not only be moved ( relocated ), and swapped to disk ( virtualized ), but with the ability to swap in register files ( a complete set of 8086 registers ), could support a virtual machine environment.

			Starting with the Westmere Processor core, not only were memory addresses virtualized, (VT-x) and register files virtualised, but I/O address could be virtualized (VT-d) which is direct I/O. A virtual machine can address Input/Output directly.

	These [[integrated circuit\|chips]] power on in real mode, in which they appear to be [[Intel 8086\|8086]]'s; this is for purposes of [[backward compatibility]] at the [[object code]] level. A small extension to that architecture allows them to switch into [[protected mode]], where all the extended features of the later architectures are available.		These [[integrated circuit\|chips]] power on in real mode, in which they appear to be [[Intel 8086\|8086]]'s; this is for purposes of [[backward compatibility]] at the [[object code]] level. A small extension to that architecture allows them to switch into [[protected mode]], where all the extended features of the later architectures are available.

Jnc: +cat

2018-12-16T21:44:59Z

+cat

← Older revision		Revision as of 21:44, 16 December 2018
Line 6:		Line 6:

	{{semi-stub}}		{{semi-stub}}

			[[Category: Intel Microprocessors]]

Jnc: A good start

2018-10-22T18:54:50Z

A good start

New page

'''Real mode''', on the [[Intel 80286|80286]] and later members of the [[Intel x86]] line, refers to a mode of the [[Central Processing Unit|CPU]] in which the extended [[architecture]]s of the later chips, including hardware support for [[virtual memory]], is ''not'' enabled.

These [[integrated circuit|chips]] power on in real mode, in which they appear to be [[Intel 8086|8086]]'s; this is for purposes of [[backward compatibility]] at the [[object code]] level. A small extension to that architecture allows them to switch into [[protected mode]], where all the extended features of the later architectures are available.

Real mode in the later x86 machines is almost entirely the same as the 8086, but there are minor differences (e.g. different Instruction Clock Counts).

{{semi-stub}}