The foundation for OS/2 Version 2.0 capabilities is its support for the Intel 80386 microprocessor. This support means that a powerful set of 32-bit features now becomes available to the operating system and applications, including enhanced memory management and more sophisticated multitasking.
OS/2 Version 2.0 requires the features of the Intel 80386 or compatible 32-bit microprocessors, and therefore does not run on computers that use the Intel 80286** processor, or its predecessors. In order to maintain compatibility, however, OS/2 Version 2.0 supports applications written for previous versions of OS/2 by providing both a 16-bit as well as a 32-bit application programming interface, allowing 16-bit applications to execute under OS/2 Version 2.0 without modification. The Intel 80386 can address 4 gigabytes of physical memory and up to 64 terabytes of virtual memory.
OS/2 Version 2.0 supports execution of the following types of applications:
All applications execute as protected mode processes under OS/2 Version 2.0, and are therefore provided with pre-emptive multitasking and full memory protection between processes.
Memory management is the way in which the operating system allows applications to access the system's memory. The operating system must check how much memory is available to an application, and handle the event when there is no longer any real memory left to satisfy an application's requests.
In OS/2 Version 2.0, memory management has been enhanced to provide a flat memory model, which takes advantage of the 32-bit addressing scheme provided by the Intel 80386 architecture. This means that through memory management, the system's memory is seen as one large linear address space of 4GB. This 32-bit programming environment is free from the limitations and inherent complexity of the segmented memory model used by DOS and previous 16-bit versions of OS/2. Memory management within applications is greatly simplified, allowing applications to be developed faster, with better performance due to reduced memory manipulation overhead. Through the use of the flat memory model, applications may be more easily ported to or from other operating system platforms.
Task Management, the management of processes and threads executing in a system, is greatly simplified and streamlined under OS/2 Version 2.0. This is due primarily to the fact that support for processes executing in real mode (such as the DOS Compatibility Box in previous versions of OS/2) is no longer required, since the execution of DOS applications is supported using virtual DOS machines which run as protected mode processes under OS/2 Version 2.0.
Interrupt handling under OS/2 Version 2.0 is simplified by removal of the need to handle real mode software interrupts. Interrupts issued by DOS and Windows applications are trapped by a virtual programmable interrupt controller (VPIC) which translates the interrupts to the appropriate device access commands for the protected mode environment. The virtual programmable interrupt controller is described in Device Drivers.