Category : Alternate Operating Systems - Quarterdeck DesqView, CP/M, etc
Archive   : QWHITE13.ZIP
Filename : VCPI.TEC

Output of file : VCPI.TEC contained in archive : QWHITE13.ZIP

ID:VC VCPI DOS Extenders
Quarterdeck Technical Note #103 Filename: VCPI.TEC
by Daniel Travison CompuServe: VCPI.TEC
Last revised: 3/09/92 Category: API

Subject: A brief description of the Virtual Control Program Interface, with a
listing of makers of some popular DOS Extenders.

The VCPI (Virtual Control Program Interface) specification was developed
to allow multiple protected mode control programs to coexist and interact
within a single 80386(486) system. The specification consists of two parts:
a VCPI server and several VCPI clients. The VCPI clients request memory and
mode switching services from the VCPI server.
In a DESQview 386 system, the VCPI server is implemented within QEMM-386
while the DOS Extended applications become VCPI clients. When the DOS Extended
application requires memory services it calls upon the VCPI server to perform
them. When QEMM-386 is not present, the DOS Extender performs the services
for itself.
The end result is that DESQview is able to run a mix of real mode and DOS
Extended (protected mode) applications concurrently on an 80386/486.
80286 systems may run multiple 286 DOS Extended applications only if the
DOS Extenders utilize XMS services. 286 DOS Extended applications may also be
run with QEMM-386 as the VCPI Server on 80386/486 systems.
There are several DOS Extenders on the market. The following is a list
of the companies that I am aware of that produce DOS Extenders for sale.
There may be other companies currently shipping, or are planning to ship, DOS
Extender tools.

Company 286 DOS Extenders 386 DOS Extenders
Name (16-bit protected mode) (32-bit protected mode)

Ergo Computing, Inc. OS286 OS386
One Intercontinental Way
Peabody, MA 01960
Corp: 508 535-7510
Sales: 800 633-1925
Fax: 508 535-7512

Phar Lap 386 DOS Extender 60
Aberdeen Avenue
Cambridge, MA 02138

Rational Systems, Inc. D16M
220 North Main Street
Natick, MA 01760

Phar Lap Notes:

The A20 must be enabled at all times. Run the program inside DESQview using
XDV.COM or ensure that QEMM is ON. An XMS driver (QEXT.SYS or HIMEM.SYS) or
VDISK will accomplish the same purpose.

*This technical note may be copied and distributed freely as long as it*
*is distributed in its entirety and it is not distributed for profit. *
* Copyright (C) 1990-2 by Quarterdeck Office Systems *
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