Execution Pipeline
2-9
18524C/0—Nov1996
AMD-K5 Processor Technical Reference Manual
dependencies are resolved using forwarding at all execution
units. Antidependencies (in which later instructions produce a
value that overwrites one used by an earlier instruction) are
removed automatically by buffering operands—or tags that
point to operands—at reservation stations. Output dependen-
cies (in which later instructions must be seen by software to
complete after earlier instructions in order to leave the correct
value in a register) are resolved by the reorder buffer.
Reservation stations are supplied with operands over eight 41-
bit operand buses. Execution results are sent to the reorder
buffer (ROB) over five 41-bit result buses. Tags forwarded to
the execution units represent results to watch for on one of the
result buses.
No special compiler optimizations are required for high-perfor-
mance execution on the AMD-K5 processor.
Integer/Shift Units
Two ALUs perform integer, logic, and shift operations. Both
ALUs have two-entry reservation stations. Table 2-1 shows the
types of ROPs executed by each ALU. Unlike the Pentium pro-
cessor, the AMD-K5 processor has few restrictions on the pair-
ing of integer instructions needed to use both integer units in
parallel.
Table 2-1. ALU Instruction Classes
Instruction Class
ALU0
ALU1
Addition
Yes
Yes
Subtraction
Yes
Yes
Logical
Yes
Yes
Compare
Yes
Yes
Packed BCD
Yes
No
Unpacked BCD
Yes
No
Special (ADDC, SUBB)
Yes
No
Shift
No
Yes
Divide
Yes
No
Summary of Contents for AMD-K5
Page 1: ...AMD K5 Processor Technical Reference Manual TM...
Page 10: ...x AMD K5 Processor Technical Reference Manual 18524C 0 Nov1996...
Page 24: ...1 4 Overview AMD K5 Processor Technical Reference Manual 18524C 0 Nov1996...
Page 54: ...2 30 Internal Architecture AMD K5 Processor Technical Reference Manual 18524C 0 Nov1996...
Page 116: ...4 26 Performance AMD K5 Processor Technical Reference Manual 18524C 0 Nov1996...
Page 356: ...6 44 System Design AMD K5 Processor Technical Reference Manual 18524C 0 Nov1996...
Page 380: ...7 24 Test and Debug AMD K5 Processor Technical Reference Manual 18524C 0 Nov1996...
Page 396: ...A 16 AMD K5 Processor Technical Reference Manual 18524C 0 Nov1996...
Page 406: ...I 10 Index AMD K5 Processor Technical Reference Manual 18524C 0 Nov1996...