Intel 80286 Features of 80286 24 bit address

Intel 80286

Features of 80286 • • 24 -bit address bus. Able to address 16 MB of physical memory. 1 GB of virtual memory. It has a MMU[memory management unit] It operates in 2 modes Real address mode Protected virtual address mode

BLOCK DIAGRAM OF 80286 1)Address unit 2)Bus unit 3)Instruction unit 4)Execution unit

ADDRESS UNIT address unit calculates the address of ü The address unit calculates the physical instructions data. physical& address of instructions & ü Thedata. address computed by AU is handed over to BU. The address computed by AU is handed over to BU.

BUS UNIT address unit calculates the ü The It fetches instruction bytes from the memory. physicalareaddress ofadvance[Instruction instructions & ü Instructions fetched in Pipelining]. data. ü These fetched instructions are arranged in a 6 -byte The address prefetch queue computed by AU is handed over to BU.

INSTRUCTION UNIT ü The pre fetch forwards the instructions The 6 -byte address unitqueue calculates the arranged in it to the IU. of instructions & physical address ü It accepts instructions from prefetch queue & an data. instruction decoder decodes them one by one. The address computed byonto AU aisdecoded ü Decoded instructions are latched instruction handedqueue. over to BU.

EXECUTION UNIT ü The of the decoding circuit is given Theo/paddress unit calculates theto EU which is responsible for executing the instructions received physical address of instructions & from the decoded instruction queue. ü ALUdata. carries all the arithmetic & logic operations. The address computed by AU is handed over to BU.

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