RM5261A-300-HI PMC [PMC-Sierra, Inc], RM5261A-300-HI Datasheet - Page 17

• Manufacturer Part Number: RM5261A-300-HI
• Manufacturer: PMC [PMC-Sierra, Inc]

Proprietary and Confidential to PMC-Sierra, Inc and for its Customer’s Internal Use
Document ID: PMC-2002240, Issue 2
3.13 Virtual to Physical Address Mapping
The RM5261A provides three modes of virtual addressing:
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•
•
This mechanism allows system software to provide a secure environment for user processes. Bits
in the CP0 register Status determine which virtual addressing mode is used. In the user mode, the
RM5261A provides a single, uniform virtual address space of 1 TB (2 GB in 32-bit mode).
When operating in the kernel mode, four distinct virtual address spaces, totalling over 2.5 TB (4
GB in 32-bit mode), are simultaneously available and are differentiated by the high-order bits of
the virtual address.
The RM5261A processors also support a supervisor mode in which the virtual address space over
2 TB (2.5 GB in 32-bit mode), divided into three regions based on the high-order bits of the virtual
address.
When the RM5261A is configured as a 64-bit microprocessor, the virtual address space layout is
an upward compatible extension of the 32-bit virtual address space layout.
Figure 5 shows the address space layout for 32-bit operation
Figure 5
0xFFFFFFFF Kernel virtual address space
0xE0000000
0xDFFFFFFF Supervisor virtual address space
0xC0000000
0xBFFFFFFF Uncached kernel physical address space
0xA0000000
0x9FFFFFFF Cached kernel physical address space
0x80000000
0x7FFFFFFF User virtual address space
0x00000000
user mode
kernel mode
supervisor mode
Kernel Mode Virtual Addressing (32-bit)
(kseg3)
Mapped, 0.5GB
(ksseg)
Mapped, 0.5GB
(kseg1)
Unmapped, 0.5GB
(kseg0)
Unmapped, 0.5GB
(kuseg)
Mapped, 2.0GB
RM5261A™ Microprocessor with 64-Bit System Bus Data Sheet
Preliminary
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