Specifications

Computer Architecture and Maintenance (G-Scheme-2014)

Other general purpose registers

These registers have no specific purpose, but are generally used for the quick storage of

pieces of data that are required later in the program execution. In the model used here

these are assigned the names A and B, with suffixes of L and U indicating the lower

and upper sections of the register respectively.

Modes of Operation of CPU

Q.List and Describe Modes of Operation of CPU

Ans. All Intel and Intel-compatible processors from the 386 on up can run in several

modes. Processor modes refer to the various operating environments and affect the

instructions and capabilities of the chip. The processor mode controls how the

processor sees and manages the system memory and the tasks that use it.

The following table summarizes the processor modes and submodes:

Mode Real IA-32 IA-32e

Submode N/A

Protected

Virtual real

64-bit

compatibility

OS Required 16-bit

32-bit

64-bit

Software 16-bit

32-bit

16-bit

64-bit

32-bit

Memory Address Size 24-bit

32-bit

24-bit

64-bit

32-bit

Default Operand Size 16-bit

32-bit

16-bit

32-bit

32/16-bit

16-bit

64-bit

32-16-bit

*IA-32e (64-bit extension mode) is also called x64, AMD64, x86-64, or

EM64T.

Real Mode

Real mode is sometimes called 8086 mode because it is based on the 8086 and

8088 processors. The original IBM PC included an 8088 processor that could execute 16-

Prepared By – Prof. Manoj.kavedia (9860174297 – 9324258878 ) (www.kavediasir.yolasite.com)