Data Structures and Memory Layout
D.2 Restart Parameter Block (RPB)
Table D–2 (Cont.) Restart Parameter Block Fields
(R11)+ Field Name
Description
44:
RPB$Q_PFNMAP
The PFN bitmap is an array of bits, where each
bit has the value "1" if the corresponding page
of memory is valid, or has the value "0" if the
corresponding page of memory contains a memory
error. Through use of the PFNMAP, the operating
system can avoid memory errors by avoiding
known bad pages altogether. The memory bitmap
is always page-aligned, and describes all the pages
of memory from physical page #0 to the high
end of memory, but excluding the PFN bitmap
itself and the Q–bus map registers. If the high
byte of the bitmap spans some pages available
to the operating system and some pages of the
PFN bitmap itself, the pages corresponding to the
bitmap itself will be marked as bad pages. The
first longword of the PFNMAP descriptor contains
the number of bytes in the PFNMAP; the second
longword contains the physical address of the
bitmap.
4C:
RPB$L_PFNCNT
Count of "good" pages of physical memory, but
not including the pages allocated to the Q22–bus
scatter/ gather map, the console scratch area, and
the PFN bitmap at the top of memory.
50:
RPB$L_SVASPT
0.
54:
RPB$L_CSRPHY
Physical address of CSR for boot device.
58:
RPB$L_CSRVIR
0.
5C:
RPB$L_ADPPHY
Physical address of ADP (really the address of
QMRs - ^x800 to look like a UBA adapter).
60:
RPB$L_ADPVIR
0.
64:
RPB$W_UNIT
Unit number of boot device.
66:
RPB$B_DEVTYP
Device type code of boot device.
67:
RPB$B_SLAVE
Slave number of boot device.
(continued on next page)
D–8 Data Structures and Memory Layout
