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System Initialization and Acceptance Testing (Normal Operation)
4.8 Operating System Restart
7. Dispatch to the restart address, RPB$L_RESTART, with :
SP
Physical address of the RPB plus 512
AP
Halt code
PSL
041F0000
PR$_MAPEN
0
If the restart is successful, the operating system must clear CPMBX<3>(RIP).
If restart fails, the firmware prints "Restart failure." on the system console.
4.8.1 Locating the RPB
The RPB is a page-aligned control block which can be identified by the first
three longwords. The format of the RPB "signature" is shown in Figure 4–6.
(Refer to Table D–2 in Appendix D for a complete description of the RPB.)
Figure 4–6 Locating the Restart Parameter Block
physical address of the RPB
physical address of the restart routine
checksum of first 31 longwords of restart routine
RPB: +00
+04
+08
MLO-008458
The firmware uses the following algorithm to find a valid RPB:
1. Search for a page of memory that contains its address in the first longword.
If none is found, the search for a valid RPB has failed.
2. Read the second longword in the page (the physical address of the restart
routine). If it is not a valid physical address, or if it is zero, return to step
1. The check for zero is necessary to ensure that a page of zeros does not
pass the test for a valid RPB.
3. Calculate the 32 bit twos-complement sum (ignoring overflows) of the first
31 longwords of the restart routine. If the sum does not match the third
longword of the RPB, return to step 1.
4. A valid RPB has been found.
4–40 System Initialization and Acceptance Testing (Normal Operation)