
MOTOROLA
Chapter 6. Memory Management
6-35
Page Table Search Operation
Table 6-11 describes the bit settings for the DCMP and ICMP registers.
6.5.2.1.3
Primary and Secondary Hash Address Registers (HASH1 and
HASH2)
HASH1 and HASH2 contain the physical addresses of the primary and secondary PTEGs
for the access that caused the TLB miss exception. Only bits 7–25 differ between them. For
convenience, the processor automatically constructs the full physical address by routing
bits 0–6 of SDR1 into HASH1 and HASH2 and clearing the lower six bits. These registers
are read-only and are constructed from the contents of the DMISS or IMISS register. The
format for HASH1 and HASH2 is shown in Figure 6-13.
Figure 6-13. HASH1 and HASH2 Registers
Table 6-12 describes the bit settings of the HASH1 and HASH2 registers.
6.5.2.1.4
Required Physical Address Register (RPA)
The RPA is shown in Figure 6-14. During a page table search operation, the software must
load the RPA with the second word of the correct PTE. When the
tlbld
or
tlbli
instruction
is executed, data from IMISS and ICMP (or DMISS and DCMP) and the RPA registers is
merged and loaded into the selected TLB entry. The TLB entry is selected by the effective
address of the access (loaded by the table search software from the DMISS or IMISS
register) and SRR1[WAY].
Table 6-11. DCMP and ICMP Bit Settings
Bits
Name
Description
0
V
Valid bit. Set by the processor on a TLB miss exception.
1–24
VSID
Virtual segment ID. Copied from VSID field of corresponding segment
register.
25
H
Hash function identifier. Cleared by the processor on a TLB miss exception.
26–31
API
Abbreviated page index. Copied from API of effective address.
Table 6-12. HASH1 and HASH2 Bit Settings
Bits
Name
Description
0–6
HTABORG[0–6]
Copy of the upper 7 bits of the HTABORG field from SDR1
7–25
Hashed page address
Address bits 7–25 of the PTEG to be searched
26–31
—
Reserved
Reserved
HTABORG
Hashed Page Address
0 0 0 0 0 0
0
6
7
25
26
31
F
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