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User’s Manual
IBM PowerPC 750GX and 750GL RISC Microprocessor
gx_01.fm.(1.2)
March 27,2006
PowerPC 750GX Overview
Page 25 of 377
1.2 750GX Microprocessor Features
This section lists features of the 750GX. The interrelationship of these features is shown in Figure 1-1 on
page 25.
Major features of 750GX are:
• High-performance, superscalar microprocessor.
– As many as four instructions can be fetched from the instruction cache per clock cycle.
– As many as two instructions can be dispatched and completed per clock.
– As many as six instructions can execute per clock (including two integer instructions).
– Single-clock-cycle execution for most instructions.
• Six independent execution units and two register files.
– BPU featuring both static and dynamic branch prediction.
• 64-entry (16-set, 4-way set-associative) branch target instruction cache (BTIC), a cache of
branch instructions that have been encountered in branch/loop code sequences. If a target
instruction is in the BTIC, it is fetched into the instruction queue a cycle sooner than it can be
Figure 1-1. 750GX Microprocessor Block Diagram
+
+
Ifetch
Branch Processing
BTIC
64 Entries
+ x ÷
FPSCR
FPSCR
CTR
LR
BHT
Data MMU
Instruction MMU
PA
EA
+ x ÷
Instruction Control Unit
Unit
Instruction Queue
(6 Words)
2 Instructions
Reservation Station
Reservation Station Reservation Station
Integer Unit 1
System Register
Unit
Dispatch Unit
64-Bit
(2 Instructions)
SRs
ITLB
(Shadow)
IBAT
Array
32-KB
I Cache
Tags
128-Bit
(4 Instructions)
32-Bit
Floating-Point
Unit
Rename Buffers
(6)
FPR File
32-Bit
64-Bit
Reservation Station
(2 Entry)
Load/Store Unit
(EA Calculation)
Store Queue
GPR File
Rename Buffers
(6)
32-Bit
SRs
(Original)
DTLB
DBAT
Array
Completion Unit
Reorder Buffer
(6 Entry)
60x Bus Interface Unit
Instruction Fetch Queue
L1 Castout Queue
Data Load Queue
L2 Cache
32-Bit Address Bus
64-Bit Data Bus
Integer Unit 2
L2CR
1 MB
SRAM
Tags
32-KB
D Cache
Reservation Station
L2 Tag
(2 Entry)
64-Bit
256-Bit
60x Bus
256-Bit
64-Bit
64-Bit
64-Bit
Additional Features:
• Time Base Cntr/
Decrementer
• Clock Multiplier
• JTAG/COP Interface
• Thermal/Power
Management
• Performance Monitor
Interrupt Logic
CR