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| CATEGORIES ABOUT DOS PROTECTED MODE INTERFACE | |
| x86 memory management | |
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This service can be 16-bit, 32-bit, or "universal" and is called the ''DPMI kernel'', ''DPMI host'', or ''DPMI server''. It is provided either by the host operating system (''virtual DPMI host'') or by a DOS Extender (''real DPMI host''). The DPMI kernel can be part of a DOS extender such as in DOS4GW or DOS/32A , or separate, like CWSDPMI or HDPMI . The first DPMI specification drafts were published in 1989 . Version 0.9 was published in 1990 by the DPMI Committee, and it was again extended in 1991 with version 1.0. An additional feature called "True DPMI" or "DOS API translation" was proposed in the version 0.9 drafts, but never became part of the official specification, nevertheless, it is featured by some products. The DPMI specification is available from Intel Literature Sales as well as online. Since version 1.0 was never implemented in Windows , many programs and DOS extenders were written to version 0.9 only. The most famous separate DPMI kernel is probably CWSDPMI, however, it supports DPMI 0.9 only and no "DOS API translation". A newer product called HDPMI provides "DOS API translation" and almost complete DPMI 1.0 implementation. Currently DPMIONE is the only standalone DPMI host which supports DPMI 1.0 completely. VCPI VCPI (Virtual Control Program Interface) was an earlier and incompatible method for doing the same thing as DPMI and was limited to 32-bit mode. VCPI was provided by an Expanded Memory manager in DOS (e.g. CEMM , QEMM , later EMM386 ). It was eclipsed by DPMI, most notably because it was not supported for DOS programs run in Windows 3.0's native Protected Mode (called ''386 enhanced mode'') and because VCPI runs programs in Ring 0, which defeated the purpose of x86 protection. It also did not work with OS/2 2.0 and later. Windows 3.x only supported VCPI in Standard and Real modes. Earlier Windows/386 2.1 was not compatible with DOS extenders at all. VCPI also had a more limited scope in that it allowed a protected mode DOS program to run only when the program was started from DOS already running inside a Virtual 8086 Mode task. (This was typically accomplished through a Memory Manager operating as a ''virtual {Link without Title} control program'' for the processor.) Because the virtual 8086 mode isolates programs from the hardware, it is not possible for a program to switch to protected mode without some support from the control program. EXTERNAL LINKS
''This article was originally based on material from the Free On-line Dictionary Of Computing , used with . Update as needed.'' |
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