Filter
Top Products
Architecture
21
2.6.2 Direct segment mapping
The R3900 Processor Core includes a direct segment mapping MMU. The following virtual address
spaces are available depending on the processor mode (Figure 2-8 shows the address mapping).
(1) User mode
One 2 Gbyte virtual address space (kuseg) is available. Virtual addresses from 0x0000 0000
to 0x7FFF FFFF are translated to physical addresses 0x4000 0000 to 0xBFFF FFFF,
respectively.
(2) Kernel mode
The kernel mode address space is treated as four virtual address segments. One of these is
the same as the kuseg space in user mode; the remaining three are the kernel segments kseg0,
kseg1 and kseg2.
(a) kuseg
This is the same as the virtual address space available in user mode. Address
translation is also the same as in user mode. The upper 16 Mbytes of kuseg is
reserved for on-chip resources and is not cacheable.
(b) kseg0
This is a 512 Mbyte segment spanning virtual addresses 0x8000 0000 to 0x9FFF
FFFF. Fixed mapping of this segment is made to physical addresses 0x0000 0000 to
0x1FFF FFFF, respectively. This area is cacheable.
(c) kseg1
This is a 512 Mbyte segment from virtual address 0xA000 0000 to 0xBFFF FFFF.
Fixed mapping of this segment is made to physical address 0x0000 0000 to 0x1FFF
FFFF, respectively. Unlike kseg0, this area is not cacheable.
(d) kseg2
This is a 1 Gbyte linear address space from virtual addresses 0xC000 0000 to 0xFFFF
FFFF. The upper 16 Mbytes of kseg2 are reserved for on-chip resources and are not
cacheable. Of this reserved area, 0xFF20 0000 to 0xFF3F FFFF is a 2 Mbyte
reserved area intended for use as a debugging monitor area and for testing.