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Encyclopedia > QEMM

QEMM (sometimes pronounced IPA: [kwɛm], though not by those who developed it), the Quarterdeck Expanded Memory Manager by Quarterdeck, was the most popular third party memory manager for the DOS operating system. For information on how to read IPA transcriptions of English words see here. ... Quarterdeck Office Systems, later Quarterdeck Corporation, was an American computer software company. ... A memory manager is a part of a computer program which accepts requests from the program to allocate and deallocate chunks of memory. ... ‹ The template below has been proposed for deletion. ... An operating system (OS) is a computer program that manages the hardware and software resources of a computer. ...

Contents

Product

Originally, it was called QEMM-386, and had a complementary product called QRAM that worked in a similar manner on Intel 80286's that had some specific Chips and Technologies chipsets. The 386 was dropped when the Intel Pentium was released. QEMM-386 and DESQview could cooperate and when shipped as a bundle were called DESQview 386. An Intel 80286 Microprocessor AMD 80286 with 12 Mhz. ... Chips and Technologies was the first fabless semiconductor company, a model developed by its founder Gordon Campbell. ... A chipset is a group of integrated circuits (chips) that are designed to work together, and are usually marketed as a single product. ... Pentium MMX - top view The Pentium is a fifth-generation x86 architecture microprocessor by Intel which first shipped on March 22, 1993. ... DESQview was a text mode multitasking program developed by Quarterdeck Office Systems which enjoyed modest popularity in the late 1980s and early 1990s. ...


QEMM provided access to the Upper Memory Blocks (UMBs), Expanded Memory Specification (EMS) memory and Extended Memory Specification (XMS) memory. Many DOS programs required a large amount of conventional memory, and QEMM helped to increase the amount of free conventional memory by loading programs into UMBs and the HMA, the first 64K (minus 16 bytes) of physical extended memory. Many programs, such as Lotus 1-2-3, early versions of Microsoft Windows, and many games, also used the EMS and XMS memory. The Upper Memory Area (UMA) is a feature of the design of IBM PC-compatible x86 computers. ... EMS or Expanded Memory Specification is an IBM PC memory paging scheme enabling access to memory other than conventional memory in real mode, through the use of an add-on peripheral holding the additional memory. ... XMS or Extended Memory Specification is the specification describing the use of IBM PC extended memory in real mode for storing data (but not executable code). ... To meet Wikipedias quality standards, this article or section may require cleanup. ... The High Memory Area (HMA) is the RAM area consisting of the first 64 kilobytes (KB), minus 16 bytes, of the extended memory on an IBM PC or compatible microcomputer. ... Extended memory refers to memory above the first megabyte of address space in an IBM PC with an 80286 or later processor. ... Lotus 1-2-3 is a spreadsheet program from Lotus Software (now part of IBM). ... Microsoft Windows is the name of several families of proprietary operating systems by Microsoft. ...


Competitors

The principal competitors of QEMM were BlueMax/386Max, and HeadRoom/NetRoom. However, QEMM outperformed everything on the market - enabling 634 KB of free conventional memory in some cases. QEMM is considered by many to be one of the most robust and technically elegant pieces of software written for the PC during its time period. 386MAX (written as 386MAX, pronounced 386-to-the-max) was a computer memory manager for DOS-based personal computers. ... Headroom (band) is the name of a band HeadRoom is the name of a headphone equipment company Headroom is a term used in signal processing (audio, data, etc) to refer to the maximum allowable signal level before compression or distortion. ...


Compaq DOS 3.31, released in November 1987, was the first DOS operating system to bundle technology similar to QEMM-386 with the OS itself, incorporating a 386-mode EMS manager called CEMM. QEMM was the first V86 memory manager on the market. Compaq Computer Corporation is an American personal computer company founded in 1982, and now a brand name of Hewlett-Packard. ... An operating system (OS) is a computer program that manages the hardware and software resources of a computer. ... CEMM, for Compaq Expanded Memory Manager was probably the first so-called PC memory manager for Intel 80386 CPUs, able to transform extended memory into EMS expanded memory by using the virtual memory features and the virtual 8086 mode of the CPU. It was present in Compaq DOS 3. ...


DOS equivalents

Microsoft released comparable but simpler memory managers of its own - HIMEM.SYS for XMS and EMM386.EXE for EMS with MS-DOS 4.01 in 1989; earlier Windows/386 2.1 included a built-in EMM which offered EMS to DOS windows during Windows sessions only. These versions could not yet create Upper Memory Blocks. Digital Research's DR-DOS 5.0 (1990) was the first non-vendor-specific DOS to offer the UMB technology, incorporating a 386-mode XMS/EMS manager also called EMM386. MS-DOS finally offered UMBs in 1991 with version 5.0. MS-DOS's EMM386 required HIMEM to be loaded first, while DR-DOS's EMM386 fulfilled both roles and did not need a separate XMS driver, which was still provided but only needed on 80286-based machines (HIDOS.SYS). Windows 2. ... The Upper Memory Area (UMA) is a feature of the design of IBM PC-compatible x86 computers. ... Digital Research, Inc. ... DR-DOS is a PC DOS-compatible operating system for IBM PC-compatible personal computers, originally developed by Gary Kildalls Digital Research and derived from CP/M-86. ... EMM386 was Microsofts expanded memory manager, which created expanded memory using extended memory on Intel 80386 CPUs. ...


Neither DR's nor MS's memory managers were as capable as QEMM - for example, both required Upper Memory Blocks to be manually discovered and included, whereas QEMM could do this quite satisfactorily on its own. QEMM also did not require one to predefine how much memory should become EMS and how much should be XMS, therefore it was not necessary to juggle boot configurations. However, although QEMM still usually freed up more conventional memory than EMM386 did, Microsoft finally automated the process of UMB optimisation in DOS 6 with the memmaker utility, and QEMM's market share began to slide.


Windows transition

While popular when DOS programs were the mainstream, QEMM eventually became irrelevant as Windows programs replaced DOS programs. The final version was QEMM 97, which was compatible with Windows 95 and later Windows 98/ME, but by this point, DOS applications were largely obsolete and thus so was DOS memory optimisation. Windows 95 is a consumer-oriented graphical user interface-based operating system. ... Windows 98 (codenamed Memphis) is a graphical operating system released on June 25, 1998 by Microsoft and the successor to Windows 95. ... Windows Me (IPA pronunciation: ), also known as Windows Millennium Edition is a hybrid 16-bit/32-bit graphical operating system released on September 14, 2000 by Microsoft. ...


When Windows 3.0 (or later) started in 386 Enhanced mode, it asked all memory managers (and possibly other TSR programs) to shut down, and took over their role for the duration of the Windows session. Indeed, it is not possible to have multiple protected-mode kernels at once. So QEMM was not actually running together with Windows. As part of the shutdown sequence related to Windows startup, memory managers could however tell Windows to load specific VxD-type device drivers which would take over their original functionality during the Windows session. For example, QEMM was shipped with WINHIRAM.VXD and WINSTLTH.VXD. They would also inform Windows about the specific memory mappings they have established, which Windows would then import (the so-called Global EMM import function). Terminate and Stay Resident (TSR) computer programs were the only way to achieve a primitive sort of multitasking (usually just task-switching) using the DOS operating system. ... In Microsoft computing, a VxD is a virtual device driver. ...


See also

CEMM, for Compaq Expanded Memory Manager was probably the first so-called PC memory manager for Intel 80386 CPUs, able to transform extended memory into EMS expanded memory by using the virtual memory features and the virtual 8086 mode of the CPU. It was present in Compaq DOS 3. ... Real mode (also called real address mode in Intels manuals) is an operating mode of 80286 and later x86-compatible CPUs. ... For efficiency reasons, the 80286 and later X86 processors use the base address stored in their internal descriptor cache whenever accessing memory, regardless if they are operating in real or protected mode. ... Protected mode is an operational mode of x86-compatible CPUs of the 80286 series or later. ... To meet Wikipedias quality standards, this article or section may require cleanup. ... Extended memory refers to memory above the first megabyte of address space in an IBM PC with an 80286 or later processor. ... XMS or Extended Memory Specification is the specification describing the use of IBM PC extended memory in real mode for storing data (but not executable code). ... EMS or Expanded Memory Specification is an IBM PC memory paging scheme enabling access to memory other than conventional memory in real mode, through the use of an add-on peripheral holding the additional memory. ... The High Memory Area (HMA) is the RAM area consisting of the first 64 kilobytes (KB), minus 16 bytes, of the extended memory on an IBM PC or compatible microcomputer. ... DESQview was a text mode multitasking program developed by Quarterdeck Office Systems which enjoyed modest popularity in the late 1980s and early 1990s. ...

External links

  • QEMM download page This is the working link now.

  Results from FactBites:
 
qemm (0 words)
The regions with the status "OK" mean that QEMM is dealing with it correctly.
The regions with the status of "Include" mean that QEMM is not using the region
that the information provided by "qemm analysis" may be accurate and usable.
QEMM (237 words)
QEMM, the Quarterdeck Expanded Memory Manager by Quarterdeck, was a popular memory manager for the DOS operating system.
QEMM provides access to the Upper Memory Area (UMA), Expanded Memory Specification (EMS) memory and Extended Memory Specification (XMS) memory.
Versions of QEMM were released into the era of Windows 98, also being compatible with it.
  More results at FactBites »

 
 

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