TITLE: OS/2 Gets Device Support
IBM finally makes it easy for hardware vendors to support OS/2
Perhaps the most notable improvement in OS/2 2.1 over version 2.0 is the newer
version's dramatically increased support for third-party expansion hardware.
For example, for the first time ever, I'm able to run my ATI Graphics Ultra
Plus in 1280- by 1024-pixel-resolution mode, with 256 colors. Users of
S3-based video boards are reporting similar success. Admittedly, these drivers
are in beta, but they will soon be generally available.
   By the time you read this, OS/2 will likely support most of the
state-of-the-art video accelerator chip sets from companies such as S3, ATI,
and Weitek. It will also claim support for non-SCSI CD-ROM drives, 24-bit
color printers, scanners, touchscreens, and a host of other input and output
   This situation is unusual for OS/2, to say the least. For most of its
existence, the operating system has lacked meaningful support for third-party
hardware. The major reason for this situation has been the lack of a DDK
(device-driver toolkit) from IBM. OS/2 device drivers are difficult to write
under the best of circumstances. Without samples, they are nearly impossible.
Driver History
When OS/2 2.0 was released, the only existing OS/2 device-driver toolkit was
the Microsoft DDK, which Microsoft had already pulled from the market.
Moreover, many things had changed in OS/2 2.0 that precluded the use of the
Microsoft DDK with this new version. The kernel debugger, which was
version-specific, was not able to work with OS/2 2.0. In addition, IBM
replaced the Microsoft LADDR (Layered Device Driver) architecture with the ADD
(Adapter Device Driver) architecture, and the Microsoft Strategy 2 disk driver
interface was replaced by IBM's EDDI (Extended Disk Driver Interface).
   Changes in DOS compatibility also affected device drivers. OS/2 1.x
supported only one DOS session, in which the processor actually operated in
real mode. OS/2 2.0, however, introduced multiple VDMs (virtual DOS machines),
which allowed each DOS program to run in its own 1-MB memory space, completely
unaware of any other running applications. These programs needed to have
shared access to I/O devices even though they assumed that they had exclusive
access to them.
   IBM's solution is the VDD, or virtual device driver, which arbitrates
ownership of the device. The VDD has also virtualized the common system
devices, such as the clock, the serial ports, and the DMA controller.
   VDDs are 32-bit DLLs, which brought up yet another problem--namely, that
there were no existing 32-bit compilers for OS/2 when version 2.0 shipped. IBM
had used a Microsoft 32-bit compiler, but it could not distribute the compiler
externally. As a result, developers were forced to write VDDs in assembly
language or not at all.
The Turnaround
As a result of all these problems, device-driver support for OS/2 2.0 was
nonexistent. Late in 1992, IBM finally realized that the lack of device
support was hindering OS/2 2.0's success and would also hurt the expected
success of OS/2 2.1.
   Under the direction of Lois Dimpfel, director of IBM's Personal Operating
Systems division, a group was formed in Boca Raton to make enhanced device
support a reality. The group consisted of device-driver experts from all parts
of IBM. Dubbed the Worldwide Industry Hardware Support department, it was
given a simple mission: do whatever was necessary to make enhanced OS/2 device
support a reality.
   The culmination of the IBM group's effort was the release of the first beta
DDK in early 1993. To ensure that it received feedback from a large number of
developers, IBM released the beta DDK for a nominal charge of $15. The DDK was
available only on CD-ROM because of its size and complexity, and it included
the previously unreleased 32-bit C compiler to make it possible to write VDDs
in C.
   The first commercial DDK was released a few months later. Dubbed the IBM
Device Driver Sourcekit 1.0, the DDK contained more than 70 device-driver
sources, as well as a large set of on-line documentation. Included were
sources to the mouse, disk, CD-ROM, serial, printer, and floppy disk drivers,
as well as a modest collection of device-driver test tools.
   In July of this year, IBM held the first-ever IBM OS/2 Device Driver
Conference. This conference was attended by more than 300 OS/2 device-driver
developers. Today, drivers for all types of devices are at last beginning to
appear, spurred on not only by the efforts of the Boca Raton team, but by the
success of OS/2 2.1 as well. IBM has put OS/2 device support back on the right
Steve Mastrianni is president of Personal Systems Software in Canton,
Connecticut. He specializes in device drivers, operating systems, and
real-time applications for OS/2 and Windows NT. You can reach him on BIX as
"smastrianni," on the Internet at smastrianni@bix.com, or on CompuServe at