(1.3) DOS and Windows Compatibility

How good is OS/2 Warp's DOS and Windows compatibility?

OS/2 1.x [see (1.2) Differences Between Versions] justifiably earned a reputation for poor DOS compatibility. Since it was hampered by the 80286, it could not run more than one DOS application at a time.

The situation changed dramatically with OS/2 2.0, and OS/2 Warp adds further refinements. OS/2 Warp Version 3 preemptively multitasks DOS and Windows (standard and enhanced mode, including Win32s) applications in separate, protected sessions.

OS/2 Warp provides a complete DOS emulation equivalent to DOS 5.0 or later. The operating system can provide each DOS application with up to 32 MB of EMS 4.0 (expanded memory), 16 MB of XMS 2.0 (extended memory), and/or 512 MB of DPMI 0.95 (DOS Protected Mode Interface extended memory), all from its pool of physical and/or virtual memory (meaning you do not have to have as much RAM in your system as your applications request). These limits are in addition to the up to 730K free conventional memory supplied to each DOS application, even after mouse and network drivers [see (3.8) Networking Products] are loaded. As in DOS 5.0 or later, DOS code and device drivers may be loaded into high memory. A 386 memory manager like QEMM is not needed -- these features are provided by OS/2 Warp directly.

The DOS emulation allows customization of device driver sets -- each DOS application shares a systemwide CONFIG.SYS and the equivalent of its own CONFIG.SYS. Also, there is a systemwide AUTOEXEC.BAT file; however, batch commands particular to each DOS application can be invoked using separate, application-specific AUTOEXEC.BAT files. And many DOS Settings are provided to fine tune [see (5.6) Performance Tuning] each DOS/Windows application's behavior (e.g. IDLE_SENSITIVITY and SESSION_PRIORITY). Most of the popular DOS/Windows applications on your hard disk will be migrated automatically when you install OS/2 Warp, so that program icons will be set up for them. Applications which are automatically recognized include over 250 of the most popular DOS, Windows, and OS/2 games.

In addition, OS/2 Warp will boot one or more specific versions of DOS in separate sessions, to assist in running particularly difficult applications (e.g. DOS networks, MSCDEX and CD-ROM drivers). So, for example, it is possible to multitask DOS 3.3, DOS 4.0, DOS 5.0, DOS 6.0, DOS 6.2, PC-DOS 6.3, DR-DOS, OS/2 Warp's DOS, and Desqview running atop DOS, all in separate sessions, either windowed or full screen, all with the same and/or separate device drivers, TSRs, environment variables, etc. DOS boot images may be stored on a hard disk. These procedures are described in the online Command Reference (under VMDISK), Master Help Index, and in the printed manual. [See also (5.9) Specific DOS Sessions.]

Standard graphics modes [generally up to VGA resolutions; see (2.2) SuperVGA Support] are supported in DOS windows, as are selectable text mode fonts. Cut/paste to/from windowed DOS applications is supported (to/from other DOS, OS/2, and Windows applications), including graphics cut/paste. Theoretically, OS/2 Warp can run up to 240 simultaneous DOS/Windows sessions; the practical maximum depends on your PC's performance.

OS/2 Warp will, in fact, run virtually all DOS applications in existence, including notorious ones such as Microsoft Flight Simulator, Wing Commander, Maple, MatLab (Version 3.5k or later), AutoCAD (Release 12 requires maintenance version C2 or later), and others. Those that do not run generally fall into the following categories:

  1. Programs that use Virtual Control Program Interface (VCPI) memory extenders or other extenders which require direct access to 80386 control registers. Since such applications are also all but incompatible with Windows, most vendors have updates for DPMI compatibility;
  2. Applications which attempt to directly address the physical sectors of an OS/2 managed nonremoveable hard disk drive. Such programs include UnErase in Norton Utilities [see (3.4) Disk Utilities]. Fortunately OS/2 Warp has a built-in UnDelete feature which is more robust than Norton's approach. (Consult the online Command Reference for information on how to enable UNDELETE);
  3. Timing sensitive DOS applications. Certain DOS programs that generate digitized sound through the PC's internal speaker may have distorted sound. High speed, real time data collection may be compromised. These problems can often be minimized or even eliminated using OS/2 Warp's DOS Settings, including the SESSION_PRIORITY setting.
  4. Certain DOS programming debuggers. DOS applications running under OS/2 Warp are not permitted to access debug registers DR0-DR7 from a DOS session. Also, DOS debuggers will not be able to set hardware breakpoints, and all read/write operations to debug registers in virtual 8086 mode will be ignored.

See (3.12) Backup Software for information on OS/2 backup issues.

DOS-based disk caching software is not required since OS/2 Warp includes a built-in, highly configurable, efficient disk cache (available even for CD-ROMs). See the online Command Reference for details.

DOS programs running under OS/2 Warp are extremely fast. A single DOS application (no other applications open) running full screen under OS/2 Warp typically achieves 95-97% of the performance it would have under native DOS. If the DOS application accesses the hard disk frequently, such as with database software, it can actually operate up to several times faster than it would if running under native DOS.

If pure DOS is absolutely required, OS/2 Warp includes a utility called the Boot Manager. The Boot Manager can provide a listing of all the operating systems available on the system and will allow selection of any one at startup, with a default after timeout. The OS/2 DualBoot method (to switch between DOS and OS/2 only) is still available as well. Consult the printed OS/2 Warp manual for instructions on how to use Boot Manager or DualBoot. Note that OS/2 Warp need not be installed on Drive C -- it can reside on other volumes [see (4.3) Hard Disk Partitioning].

Compatibility with Windows, a popular DOS extender, is provided by either Win-OS/2, an environment based on Microsoft's Windows source code, or by an actual copy of Windows 3.1, Windows 3.11, Windows for Workgroups 3.1, or Windows for Workgroups 3.11. See (1.2) Differences Between Versions for details. OS/2 Warp supports Windows 3.x enhanced mode (including Win32s) and standard mode applications, either on a full screen Windows desktop (with the familiar Program Manager and one or more Windows applications) or "seamlessly," alongside OS/2 applications on the Workplace Shell desktop. "Seamless" operation is available with all video drivers that ship with OS/2 Warp (VGA or better). [See (2.2) SuperVGA Support.]

Several icon conversion utilities can convert Windows icons for use by the OS/2 Icon Editor and/or OS/2-specific programs [see (3.2) Shareware and Freeware Sources]. (No conversion is necessary if the icons are to be used with Windows programs running under OS/2 Warp.)

OS/2 Warp directly provides all Windows enhanced mode features save one: support for Windows virtual drivers (VxD). Services provided by WINMEM32.DLL and Win32s are supported. See (0.4) Special Report on OS/2 Warp for more information.

Windows applications are well integrated into the overall OS/2 Workplace Shell environment with DDE and Clipboard hooks, and OLE (Object Linking and Embedding) is supported among Windows applications. Adobe Type Manager [see (5.5) Adobe Type Manager] comes with OS/2 Warp (for both OS/2 and Windows applications), and TrueType fonts still work fine with Windows applications. Windows screen (for a full screen desktop) and printer device drivers will work under Win-OS/2 [see (2.2) SuperVGA Support]. Such notorious Windows applications as Word, Norton Desktop (save portions described above), Toolbook, and After Dark work fine under Win-OS/2. Even applications which rely on the Windows Multimedia Extensions (supplied as part of Windows and Win-OS/2) operate without trouble. [See (3.6) Multimedia for information on the OS/2 multimedia extensions, MMPM/2.] Even the Windows applets run just fine.

OS/2 Warp's Windows support (called Win-OS/2) departs from plain Microsoft Windows in that it allows more than one Windows desktop and can preemptively (rather than cooperatively) multitask Windows applications in separate, robust, protected sessions, at the user's option. Also, both DOS and OS/2 applications can be started from the Win-OS/2 Program Manager.

In short, OS/2 Warp is generally regarded as the most DOS and Windows compatible among the new crop of 32-bit operating systems (NT included). It is also generally regarded as a better DOS multitasker than Desqview.

Related information:

(0.4)  Special Report on OS/2 Warp
(1.2)  Differences Between Versions
(2.2)  SuperVGA Support
(3.2)  Shareware and Freeware Sources
(3.4)  Disk Utilities
(3.6)  Multimedia
(3.8)  Networking Products
(3.12) Backup Software
(4.3)  Hard Disk Partitioning
(4.4)  Starting OS/2 from Diskette
(5.5)  Adobe Type Manager
(5.6)  Performance Tuning
(5.9)  Specific DOS Sessions

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