RM7000-250T View Datasheet(PDF) - PMC-Sierra

Part Name

Description

Manufacturer

RM7000-250T

RM7000™ Microprocessor with On-Chip Secondary Cache Datasheet Released

PMC-Sierra 

RM7000™ Microprocessor with On-Chip Secondary Cache Datasheet

Released

4.12 Virtual to Physical Address Mapping

The RM7000 provides three modes of virtual addressing:

• user mode

• supervisor mode

• kernel mode

This mechanism is available to system software to provide a secure environment for user

processes. Bits in the CP0 Status register determine which virtual addressing mode is used. In the

user mode, the RM7000 provides a single, uniform virtual address space of 256 GB (2 GB in 32-

bit mode).

When operating in the kernel mode, four distinct virtual address spaces, totalling 1024 GB (4 GB

in 32-bit mode), are simultaneously available and are differentiated by the high-order bits of the

virtual address.

The RM7000 processor also supports a supervisor mode in which the virtual address space is

256.5 GB (2.5 GB in 32-bit mode), divided into three regions based on the high-order bits of the

virtual address. Figure 6 shows the address space layout for 32-bit operation.

Figure 6 Kernel Mode Virtual Addressing (32-bit mode)

0xFFFFFFFF Kernel virtual address space

(kseg3)

0xE0000000 Mapped, 0.5GB

0xDFFFFFFF

0xC0000000

Supervisor virtual address space

(ksseg)

Mapped, 0.5GB

0xBFFFFFFF

0xA0000000

Uncached kernel physical address space

(kseg1)

Unmapped, 0.5GB

0x9FFFFFFF

0x80000000

Cached kernel physical address space

(kseg0)

Unmapped, 0.5GB

0x7FFFFFFF

User virtual address space

(kuseg)

Mapped, 2.0GB

When the RM7000 is configured for 64-bit addressing, the virtual address space layout is an

upward compatible extension of the 32-bit virtual address space layout.

Proprietary and Confidential to PMC-Sierra, Inc and for its Customer’s Internal Use

19

Document ID: PMC-2002175, Issue 1

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