80386 Functional Units - Intel 80386 Reference Manual

INTERNAL ARCHITECTURE
The Execution Unit in turn consists of three subunits:
• Control Unit
• Data Unit
• Protection Test Unit
Figure 2-2 shows the organization of these units. This chapter describes the function of each
unit, as well as interactioris between units. .
2.1 BUS INTERFACE UNIT
The Bus Interface Unit provides the interface between the 80386 and its environment. It
accepts internal requests for code fetches (from the Code Prefetch Unit) and data transfers
(from the Execution Unit), and prioritizes the requests. At the same time, it generates or
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EXECUTION
UNIT
REGISTERS
BARREL
SHIFTER
MULTIPLYI
DIVIDE
ALU
1
SEGMENT UNIT PAGE UNIT
SEGMENT
TRANSLATION
REGISTERS
LOOKASIDE
BUFFER
SEGMENT PAGE
TRANSLATOR TRANSLATOR
BUSUNIT
-
r--
1 1
BUS INTERFACE
1
DECODER
-
PRE FETCH
QUEUE
INSTRUCTION
..
PREFETCHER
QUEUE
DECODE UNIT PREFETCH UNIT
G30107
Figure
2-2.
80386 Functional Units
2-2