It was the first 8086-based CPU with separate, non-multiplexed address and data buses and also the first with memory management and wide protection abilities.

The 80286 used approximately 134,000 transistors in its original nMOS (HMOS) incarnation and, just like the contemporary 80186,[6] it can correctly execute most software written for the earlier Intel 8086 and 8088 processors.

[16] The CPU was designed for multi-user systems with multitasking applications, including communications (such as automated PBXs) and real-time process control.

This was a large increase, fully comparable to the speed improvements seven years later when the i486 (1989) or the original Pentium (1993) were introduced.

The 80286 also added new instructions for protected mode: ARPL, CLTS, LAR, LGDT, LIDT, LLDT, LMSW, LSL, LTR, SGDT, SIDT, SLDT, SMSW, STR, VERR, and VERW.

[18] Additionally, there was a performance penalty involved in accessing extended memory from real mode as noted below.

This would allow IBM compatibles to have advanced multitasking OSes for the first time and compete in the Unix-dominated[citation needed] server/workstation market.

To support protected mode, new instructions have been added: ARPL, VERR, VERW, LAR, LSL, SMSW, SGDT, SIDT, SLDT, STR, LMSW, LGDT, LIDT, LLDT, LTR, CLTS.

For example, in 1986 the only program that made use of it was VDISK, a RAM disk driver included with PC DOS 3.0 and 3.1.

[18] The difficulty lay in the incompatibility of older real-mode DOS programs with protected mode.

While it was possible to set up a protected-mode environment that allowed all programs access to all segments (by putting all segment descriptors into the Global Descriptor Table (GDT) and assigning them all the same privilege level), this undermined nearly all of the advantages of protected mode except the extended (24-bit) address space.

The choice that OS developers faced was either to start from scratch and create an OS that would not run the vast majority of the old programs, or to come up with a version of DOS that was slow and ugly (i.e., ugly from an internal technical viewpoint) but would still run a majority of the old programs.

The problems led to Bill Gates referring to the 80286 as a "brain-damaged" chip,[25] since it was clear that the new Microsoft Windows environment would not be able to run multiple MS-DOS applications with the 286.