26. 80386 CPU

• Year 1985.

• The 80386 and many of its successors are 32-bit CPUs.

• Internal registers are 32 bits in size.

• Unlike its predecessors, the 80386 processor can handle both 16-bit and 32-bit data.

• Supports entire instruction set of 80286.

• Adds several new instructions as well.

• Software written for the 80286 runs unchanged on the 80386, but the chip is faster.

• The 80386 implements many new hardware-level features, including

  • paged memory.

  • segmentation can be turned off (flat model).

  • support for multiple virtual 8086 processes.

  • addressing of up to 4 gigabytes of memory.

  • specialized debugging registers.