RM5261A-250-H PMC-Sierra Inc, RM5261A-250-H Datasheet - Page 11

• Manufacturer Part Number: RM5261A-250-H
• Description: RM5261A Microprocessor with 64-Bit System Bus Data Sheet Preliminary
• Manufacturer: PMC-Sierra Inc

Proprietary and Confidential to PMC-Sierra, Inc and for its Customer’s Internal Use
Document ID: PMC-2002240, Issue 2
3
3.1
3.2
3.3
Hardware Overview
The RM5261A offers a high-level of integration targeted at high-performance embedded
applications. The key elements of the RM5261A are briefly described below.
Superscalar Dispatch
The RM5261A has an asymmetric superscalar dispatch unit which allows it to issue an integer
instruction and a floating-point computation instruction simultaneously. Integer instructions
include alu, branch, load/store, and floating-point load/store, while floating-point computation
instructions include floating-point add, subtract, combined multiply-add, and convert. In
combination with its high-throughput fully pipelined floating-point execution unit, the superscalar
capability of the RM5261A provides unparalleled price/performance in computationally intensive
embedded applications.
CPU Registers
The RM5261A CPU contains 32 general purpose registers, two special purpose registers for
integer multiplication and division, a program counter, and no condition code bits. Figure 2 shows
the user visible state.
Figure 2 CPU Registers
Integer Unit
The RM5261A implements the MIPS IV Instruction Set Architecture and is therefore fully upward
compatible with applications that run on processors implementing the earlier generation MIPS I-
III instruction sets. Additionally, the RM5261A includes two implementation specific instructions
not found in the baseline MIPS IV ISA but that are useful in the embedded market place. These
instructions are integer multiply-accumulate ( MAD ) and 3-operand integer multiply ( MUL ).
The RM5261A integer unit includes thirty-two general purpose 64-bit registers, a load/store
architecture with single cycle ALU operations (add, sub, logical, shift) and an autonomous
multiply/divide unit. Additional register resources include: the HI/LO result registers for the two-
operand integer multiply/divide operations, and the program counter (PC).
General Purpose Registers
63
0
r1
r2
•
•
•
•
r29
r30
r31
0
RM5261A™ Microprocessor with 64-Bit System Bus Data Sheet
Multiply/Divide Registers
63
HI
63
LO
Program Counter
63
PC
0
0
0
Preliminary
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