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Upper Memory
In DOS memory management, the upper memory area (UMA) refers to memory between the addresses of 640 KB and 1024 KB ( 0xA0000–0xFFFFF) in an IBM PC or compatible. IBM reserved the uppermost 384 KB of the 8088 CPU's 1024 KB address space for BIOS ROM, Video BIOS, Option ROMs, video RAM, RAM on peripherals, memory-mapped I/O, and obsoleted ROM BASIC. However, even with video RAM, the ROM BIOS, the Video BIOS, the Option ROMs, and I/O ports for peripherals, much of this 384 KB of address space was unused. As the 640 KB memory restriction became ever more of an obstacle, techniques were found to fill the empty areas with RAM. These areas were referred to as upper memory blocks (UMBs). Usage The next stage in the evolution of DOS was for the operating system to use upper memory blocks (UMBs) and the high memory area (HMA). This occurred with the release of DR DOS 5.0 in 1990. DR DOS' built-in memory manager, EMM386.EXE, could perform most ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
QEMM
Quarterdeck Expanded Memory Manager (QEMM) is a memory manager produced by Quarterdeck Office Systems in the late 1980s through the late 1990s. It was the most popular third-party memory manager for the MS-DOS and other DOS operating systems. QEMM product ranges ;QRAM: A memory manager for Intel 80286 or higher CPUs. It supports Chips and Technologies chipsets. 2.02 added SHADOWRAM switch. QEXT correctly reallocates eXtended Memory Specification (XMS). It includes VIDRAM, Optimize, LOADHI from QEMM 6.02, Manifest 1.13. Earlier versions of QRAM also supported the older 8086 and 8088 CPUs. ;QEMM Game Edition: It is a version of QEMM that includes Quarterdeck GameRunner. Patches for regular QEMM do not work on QEMM Game Edition. ;QEMM MegaBundle: In the version shipped with Borland SideKick for Windows, it is a version with SideBar 1.00 (1994-08-22) and QEMM 7.5. ;DESQview 386: It includes DESQview and QEMM-386. Features/tools QEMM driver QEMM provides access to the Upper Mem ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
DOS Protected Mode Interface
In computing, the DOS Protected Mode Interface (DPMI) is a specification introduced in 1989 which allows a DOS program to run in protected mode, giving access to many features of the new PC processors of the time not available in real mode. It was initially developed by Microsoft for Windows 3.0, although Microsoft later turned control of the specification over to an industry committee with open membership. Almost all modern DOS extenders are based on DPMI and allow DOS programs to address all memory available in the PC and to run in protected mode (mostly in ring (computer security), ring 3, least privileged). Overview DPMI stands for DOS Protected Mode Interface. It is an API that allows a program to run in protected mode on 80286 series and later processors, and do the calls to real mode without having to set up these CPU modes manually. DPMI also provides the functions for managing various resources, notably Computer Memory, memory. This allows the DPMI-enabled programs to ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Virtual Control Program Interface
In computing, the Virtual Control Program Interface (VCPI) is a specification published in 1989 by Phar Lap Software that allows a DOS program to run in protected mode, granting access to many features of the processor not available in real mode. It was supplanted by DOS Protected Mode Interface (DPMI) shortly after being introduced, due in large part to VCPI's inability to work in Windows 3.0's protected mode. Overview Developed since 1987 in cooperation with Quarterdeck Office Systems and with support by A.I. Architects, Lotus Development Corp., Quadram, Qualitas and Rational Systems, VCPI is provided by an expanded memory manager in DOS (e.g. CEMM, QEMM, later EMM386) and does allow 80386 protected-mode DOS extenders to coexist with 80386 EMS expanded memory emulators. 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 ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
