Sun Microelectronics
37
5. Cache and Memory Interactions
• Some conditions, noted below, cause an otherwise supported PREFETCH to
be treated as a NOP and removed from the load buffer when it reaches the
front of the queue.
• No PREFETCH will cause a trap except:
• PREFETCH with fcn=5..15 causes an
illegal_instruction
trap, as defined in The
SPARC Architecture Manual, Version 9.
• Watchpoint, as defined in Section A.5, “Watchpoint Support,” on page 304.
• Any PREFETCHA that specifies an internal ASI in the following ranges is not
enqueued on the load buffer and is not executed:
• 40
16
..4F
16
, 50
16
..5F
16
, 60
16
..6F
16
, 76
16
, 77
16
• The following conditions cause a PREFETCH{A} to be treated as a NOP:
• PREFECTH with fcn=16..31, as defined in The SPARC Architecture Manual,
Version 9.
• A
data_access_MMU_miss
exception
• D-MMU disabled
• For PREFETCHA, any ASI other than the following 04
16
, 0C
16
, 10
16
, 11
16
,
18
16
, 19
16
, 80
16
..83
16
, 88
16
..8B
16
• Attempt to PREFETCH to a noncacheable page
• Alignment is not checked on PREFETCH{A}. The 5 least significant address
are ignored.
5.3.5.2 Implemented fcn Values
Table 5-3 lists the supported values for fcn and their meanings.
For more information, including an enumeration of the bus transaction the each
fcn value causes, see Section 14.4.5, “PREFETCH{A} (Impdep #103, 117),” on page
248.
Table 5-3 PREFETCH{A} Variants
fcn Prefetch Function
0 Prefetch for several reads
1 Prefetch for one read
2 Prefetch page
3 Prefetch for several writes
4 Prefetch for one write
5..15
illegal_instruction
trap
16..31 NOP
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