Features
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18.1SPECint95, Estimates 12.3 SPECfp95 at 400 MHz (PC755B)
15.7SPECint95, 9SPECfp95 at 350 MHz (PC745B)
733 MIPS at 400 MHz (PC755B) at 641 MIPS at 350 MHz (PC745B)
Selectable Bus Clock (12 CPU Bus Dividers up to 10x)
P
D
Typical 6.4W at 400 MHz, Full Operating Conditions.
Nap, Doze and Sleep Modes for Power Savings
Superscalar (3 Instructions per Clock Cycle) Two Instruction + Branch
4 Beta Byte Virtual Memory, 4-GByte of Physical Memory
64-bit Data and 32-bit Address Bus Interface
32-KB Instruction and Data Cache
Six Independent Execution Units
Write-back and Write-through Operations
f
INT
max = 400 MHz (TBC)
f
BUS
max = 100 MHz
Voltage I/O 2.5V/3.3V; Voltage Int 2.0V
PowerPC
755B/745B RISC
Microprocessor
PC755B/745B
Preliminary
β-site
Description
The PC755B and PC745B PowerPC
®
microprocessors are high-performance, low-
power, 32-bit implementations of the PowerPC Reduced Instruction Set Computer
(RISC) architecture, especially enhanced for embedded applications.
The PC755B and PC745B microprocessors differ only in that the PC755B features an
enhanced, dedicated L2 cache interface with on-chip L2 tags. The PC755B is a drop-
in replacement for the award winning PowerPC 750™ microprocessor and is footprint
and user software code compatible with the MPC7400 microprocessor with AltiVec
™
technology. The PC745B is a drop-in replacement for the PowerPC 740
™
micropro-
cessor and is also footprint and user software code compatible with the PowerPC
603e™ microprocessor. PC755B/745B microprocessors provide on-chip debug sup-
port and are fully JTAG-compliant.
The PC745B microprocessor is pin compatible with the TSPC603e family.
ZF suffix
PBGA255
Flip-Chip Plastic Ball Grid Array
ZF suffix
PBGA360
Flip-Chip Plastic Ball Grid Array
G suffix
CBGA255 and CBGA360
Ceramic Ball Grid Array
GS suffix
CI-CBGA255 and CI-CBGA360
Ceramic Ball Grid Array
with Solder Column Interposer (SCI)
Screening
This product is manufactured in full compliance with:
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CBGA + CI-CGA + FC-PBGA up screenings based upon Atmel standards
Full military temperature range (Tj = -55°C,+125°C)
industrial temperature range (Tj = -40°C,+110°C)
Rev. 2138A–HIREL–05/02
1
Figure 1.
PC755B Block Diagram
Simplified Block Diagram
General Description
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PC755B/745B
2138A–HIREL–05/02
Instruction Unit
Fetcher
Branch Processing
Unit
BTIC
64-Entry
BHT
CTR
LR
128-Bit
(4 Instructions)
Additional Features
¥ Time Base Counter/Decrementer
¥ Clock Multiplier
¥ JTAG/COP Interface
¥ Thermal/Power Management
¥ Performance Monitor
Instruction Queue
(6-Word)
Instruction MMU
SRs
(Shadow)
ITLB
IBAT
Array
The PC755B is targeted for low power systems and supports power management fea-
tures such as doze, nap, sleep, and dynamic power management. The PC755B
consists of a processor core and an internal L2 Tag combined with a dedicated L2
cache interface and a 60x bus.
Tags
32-Kbyte
I Cache
2 Instructions
Dispatch Unit
64-Bit
(2 Instructions)
Reservation Station Reservation Station Reservation Station
GPR File
Rename Buffers
(6)
Reservation Station
(2-Entry)
FPR File
Rename Buffers
(6)
Reservation Station
Integer Unit 1
Integer Unit 2
System Register
Unit
32-Bit
Load/Store Unit
64-Bit
+
(EA Calculation)
Store Queue
64-Bit
Floating-Point
Unit
+ x Ö
32-Bit
+
+ x Ö
FPSCR
FPSCR
CR
32-Bit
PA
Completion Unit
Reorder Buffer
(6-Entry)
Data MMU
SRs
(Original)
DTLB
EA
60x Bus Interface Unit
64-Bit
Instruction Fetch Queue
L1 Castout Queue
L2 Bus Interface
Unit
L2 Castout Queue
DBAT
Array
Tags
32-Kbyte
D Cache
Data Load Queue
L2 Controller
L2CR
32-Bit Address Bus
32-/64-Bit Data Bus
17-Bit L2 Address Bus
64-Bit L2 Data Bus
L2 Tags
Not in the PC745
PC755B/745B
General Parameters
The following list provides a summary of the general parameters of the PC755B:
Technology
Die size
Transistor count
Logic design
PC745B
PC755B
Core power supply
0.22 µm CMOS, six-layer metal
6.61 mm x 7.73 mm (51 mm
2
)
6.75 million
Fully-static Packages
Surface mount 255 Plastic Ball Grid Array (PBGA)
Surface mount 360 Plastic Ball Grid Array (PBGA)
2V ± 100 mV DC (nominal; some parts support core
voltages down to 1.8V; see Table 5 for recommended
operating conditions)
2.5V ± 100 mV DC or 3.3V ± 165 mV DC (input thresh-
olds are configuration pin selectable)
I/O power supply
Features
This section summarizes features of the PC755B’s implementation of the PowerPC
architecture. Major features of the PC755B are as follows:
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Branch Processing Unit
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Four instructions fetched per clock
One branch processed per cycle (plus resolving 2 speculations)
Up to 1 speculative stream in execution, 1 additional speculative stream in
fetch
512-entry branch history table (BHT) for dynamic prediction
64-entry, 4-way set associative Branch Target Instruction Cache (BTIC) for
eliminating branch delay slots
Full hardware detection of dependencies (resolved in the execution units)
Dispatch two instructions to six independent units (system, branch,
load/store, fixed-point unit 1, fixed-point unit 2, floating-point)
Serialization control (predispatch, postdispatch, execution serialization)
Register file access
Forwarding control
Partial instruction decode
6 entry completion buffer
Instruction tracking and peak completion of two instructions per cycle
Completion of instructions in program order while supporting out-of-order
instruction execution, completion serialization and all instruction flow
changes
Fixed Point Unit 1 (FXU1)-multiply, divide, shift, rotate, arithmetic, logical
Fixed Point Unit 2 (FXU2)-shift, rotate, arithmetic, logical
Single-cycle arithmetic, shifts, rotates, logical
Multiply and divide support (multi-cycle)
Dispatch Unit
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Decode
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Completion
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Fixed Point Units (FXUs) that share 32 GPRs for Integer Operands
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Early out multiply
Support for IEEE-754 standard single and double precision floating point
arithmetic
Hardware support for divide
Hardware support for denormalized numbers
Single-entry reservation station
Supports non-IEEE mode for time-critical operations
Executes CR logical instructions and miscellaneous system instructions
Special register transfer instructions
One cycle load or store cache access (byte, half-word, word, double-word)
Effective address generation
Hits under misses (one outstanding miss)
Single-cycle unaligned access within double word boundary
Alignment, zero padding, sign extend for integer register file
Floating point internal format conversion (alignment, normalization)
Sequencing for load/store multiples and string operations
Store gathering
Cache and TLB instructions
Big and Little-endian byte addressing supported
Misaligned Little-endian supported
Level 1 Cache structure
32K, 32 bytes line, 8-way set associative instruction cache (iL1)
32K, 32 bytes line, 8-way set associative data cache (dL1)
Cache locking for both instruction and data caches, selectable by group of
ways
Single-cycle cache access
Pseudo least-recently used (PLRU) replacement
Copy-back or Write Through data cache (on a page per page basis)
Supports all PowerPC memory coherency modes
Non-Blocking instruction and data cache (one outstanding miss under hits)
No snooping of instruction cache
Internal L2 cache controller and tags; external data SRAMs
256K, 512K, and 1-Mbyte 2-way set associative L2 cache support
Copyback or write-through data cache (on a page basis, or for all L2)
Instruction-only mode and data-only mode.
64 bytes (256K/512K) or 128 bytes (1M) sectored line size
Supports flow through (register-buffer) synchronous burst SRAMs, pipelined
(register-register) synchronous burst SRAMs (3-1-1-1 or strobeless 4-1-1-1)
and pipelined (register-register) late-write synchronous burst SRAMs
Floating-point Unit and a 32-entry FPR File
System Unit
Load/Store Unit
Level 2 (L2) Cache Interface (not implemented on PC745B)
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PC755B/745B
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PC755B/745B
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L2 configurable to direct mapped SRAM interface or split cache/direct
mapped or private memory
Core-to-L2 frequency divisors of 1, 1.5, 2, 2.5, and 3 supported
64-bit data bus
Selectable interface voltages of 2.5V and 3.3V
Parity checking on both L2 address and data
128 entry, 2-way set associative instruction TLB
128 entry, 2-way set associative data TLB
Hardware reload for TLBs
Hardware or optional software tablewalk support
8 instruction BATs and 8 data BATs
8 SPRGs, for assistance with software tablewalks
Virtual memory support for up to 4 hexabytes (2
52
) of virtual memory
Real memory support for up to 4 gigabytes (2
32
) of physical memory
Compatible with 60X processor interface
32-bit address bus
64-bit data bus, 32-bit mode selectable
Bus-to-core frequency multipliers of 2x, 3x, 3.5x, 4x, 4.5x, 5x, 5.5x, 6x, 6.5x,
7x, 7.5x, 8x, 10x supported
Selectable interface voltages of 2.5V and 3.3V.
Parity checking on both address and data busses
Low-power design with thermal requirements very similar to PC740/750.
Selectable interface voltage of 1.8V/2.0V can reduce power in output buffers
(compared to 3.3V)
Three static power saving modes: doze, nap, and sleep
Dynamic power management
LSSD scan design
IEEE 1149.1 JTAG interface
One-ship thermal sensor and control logic
Thermal Management Interrupt for software regulation of junction
temperature
Memory Management Unit
Bus Interface
Power Management
Testability
Integrated Thermal Management Assist Unit
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