The 80286 is called the second generation of microprocessor, it is more advanced to the 80186. This is the first Intel microprocessor offering multitasking and virtual memory. It is a 16-bit processor capable of addressing up to 16 MB (as it had an address but of 24-bits) of RAM and could also work with virtual memory (1GB). . It had a prefetch queue of 6 instructions. The 286 is the first “real” processor. It introduced the concept of protected mode and real mode. To ensure proper operation, we must protect the operating system and all other programs and the shared resources. The approach taken by many operating systems provide hardware support that allows us to differentiate among various modes of operation. A bit called the mode bit is added to the hardware of the computer to indicate the current mode. With the mode bit, we are able to distinguish between a task that is executed on behalf of the operating system and one that is executed on behalf of the user. The dual mode of operation provides us with the means for protecting the operating system from errant users. This is accomplished by designing some of the machine instructions that may cause harm as “privileged instructions”, these instructions are executed only in monitor mode. The 286 had an extra register called the Machine Status Register (MSW) whose lower nibble (containing D3 D2 D1 D0) defined the mode of operation and moreover it uses a four level memory protection which is an extension of the user/supervisory (protected/real) mode concept. It also had on-chip Memory Management Unit (MMU). This is also the first Intel processor that could run all of the software written for its predecessor. It has 134,000 transistors and could run at 6 to 12.5MHz