Physical memory layout.
availmem     +-----------------------+
             :                       :
             :       page pool       :
             :                       :
             |-----------------------|
             |       Page Table      |
             | (aligned to its size) |
PAGETABLE    |-----------------------|
             |                       |
             |       page pool       |
             |                       |
             |-----------------------|
             :                       :
             |   kadb, unix, etc.    |
             :                       :
             |-----------------------|
             |    Ramdisk (temp)     |       (8-16 M)
0x00100000   |-----------------------|
             |    boot code/data/etc.|       (~1M)
0x00009000   |-----------------------|
             |    boot stack         |       (8 K)
0x00007000   |-----------------------|
             |    msgbuf             |       (8 K)
0x00005000   |-----------------------|
             |    rtt, fast syscall  |       (4 K)
0x00004000   |-----------------------|
             |       Level-0         |       (16 K)
             | Interrupt handlers    |
0x00000000   +-----------------------+

               Virtual memory layout.
             /-----------------------\
             |       INVALID         |
0xFFF00000   |-----------------------|
             |       debugger        |                       (1 M)
0xFFE00000   |-----------------------|- DEBUGSTART
             :                       :
             |       Ramdisk         |                       (15 M)
             |  (debugging only)     |
             :                       :
0xFEF00000  -|-----------------------|- RAMDISK
             :                       :
             |       unused          |
             :                       :
             |-----------------------|
             |    exec args area     |  NCARGS               (1 M)
0xF3800000  -|-----------------------|- ARGSBASE
             :                       :
             |  PCI/ISA I/O SPACE    |                       (8 M)
             :   (non cacheable)     :
0xF3000000  -|-----------------------|- PCIISA_VBASE
             |       segkmap         |  SEGMAPSIZE           (16 M)
0xF2000000  -|-----------------------|
             |                       |
             :       Page Table      :  MAXPTSIZE            (32 M)
             | (may be mapped by BAT)|
0xF0000000  -|-----------------------|- PAGE_TABLE
             :                       :
             |       unused          |
             :                       :
0xEF000000  -|-----------------------|- SYSLIMIT
             :                       :
             |       Sysmap          | SYSPTSIZE             (128 M)
             :                       :
             |                       |
0xE7003000  -|-----------------------|
             |        msgbuf         |                       (8 K)
0xE7001000  -|-----------------------|- V_MSGBUF_ADDR
             |     not used (4k)     |
0xE7000000   |-----------------------|- SYSBASE
             :                       :
             |       unused          |
             :                       :
             |-----------------------|- eecontig
             |        segkp          |
             |-----------------------|- econtig
             |    vm structures      |
             | (page structures      |
             |  page hash            |
             |  memseg structures)   |
             |-----------------------|- e_data
             |       kernel data     |
             | (data sections for    |
             |  genunix, unix, rtld) |
0xE2000000  -|-----------------------|- s_data = (KERNELBASE + 32MB)
             | text sections of      |
             | kernel dynamic        |
             | modules (managed by   |
             | lokmem_alloc())       |
             |-----------------------|- e_text
             |       kernel text     |
             | (text sections for    |
             |  genunix, unix, rtld) |
0xE0001000  -|-----------------------|- s_text
             |  user copy red zone   |                       (4K)
             |       (invalid)       |
0xE0000000  -|-----------------------|- KERNELBASE
             |       user stack      |
             :                       :
             |   dynamic segments    |
             :                       :
             |       user data       |
             |-----------------------|- (user data aligned for 64K)
             |       user text       |
0x02000000   |-----------------------|
             :                       :
             |   dynamic segments    |
             :                       :
0x00010000  -|-----------------------|
             |       not used        |
0x00000000  _|_______________________|