Real mode - Revision history

Jnc: punc

2023-01-19T14:57:02Z

punc

Jnc: +See also

2021-03-02T22:13:46Z

+See also

Jnc: better word

2021-03-02T22:01:22Z

better word

Jnc: start clean-up

2021-03-02T15:31:13Z

start clean-up

ForOldHack: /* added link */

2020-07-02T01:31:42Z

‎added link

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

2020-07-02T01:29:38Z

‎redecorated: Rearranged into paragraphs. ...

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?

Jnc: +cat

2018-12-16T21:44:59Z

+cat

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}}

@@ Line 5: / Line 5: @@
 ==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.

@@ Line 19: / Line 19: @@
 * 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.
 ==External links==

← Older revision		Revision as of 22:01, 2 March 2021
Line 1:		Line 1:
−	'''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).

@@ Line 1: / Line 1: @@
-'''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).
-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.
-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.
-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==
 {{semi-stub}}
 [[Category: Intel Microprocessors]]

@@ Line 20: / Line 20: @@
 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.
 {{semi-stub}}
 [[Category: Intel Microprocessors]]

← Older revision		Revision as of 01:00, 2 July 2020
Line 1:		Line 1:
−	'''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.

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

	{{semi-stub}}		{{semi-stub}}
		+
		+	[[Category: Intel Microprocessors]]