Release 1.0, 1 July 2002
F. Chapter 5
Registers
23
After a power-on reset (
POR
), all fields of
DCUCR
, including implementation-
dependent fields, are set to 0. After a
WDR
,
XIR
, or
SIR
reset, all fields of
DCUCR
,
including implementation-dependent fields, are set to 0.
The Data Cache Unit Control Register is illustrated in
FIGURE 5-2
and described in
TABLE 5-3
. In the table, bits are grouped by function rather than by strict bit sequence.
FIGURE 5-2
DCU Control Register Access Data Format (ASI 45
16
)
TABLE 5-3
DCUCR Description
Bits
Field
Type
Use — Description
49:48
CP
,
CV
RW
Not implemented in SPARC64 V (impl. dep. #232). It reads as 0 and writes to
it are ignored.
47:42
impl. dep.
Not used. It reads as 0 and writes to it are ignored.
41
WEAK_SPCA
RW
Used for disabling speculative memory access (impl. dep. #240). When
DCUCR.WEAK_SPCA
=
1
, the branch history table is cleared and no longer
issues aggressive instruction prefetch.
During
DCUCR.WEAK_SPCA
=
1
, aggressive instruction prefetching is
disabled and any load and store instructions are considered presync
instructions that are executed when all previous instructions are committed.
Because all CTI are considered as not taken, instructions residing beyond 1
Kbyte of a CTI may be fetched and executed.
On entering aggressive instruction Prefetch disable mode, supervisor
software should issue
membar #Sync
, to make sure all in-flight instructions
in the pipeline are discarded.
During
DCUCR.WEAK_SPCA
= 1, an L2 cache flush by writing 1 to
ASI_L2_CTRL.U2_FLUSH
remains pending internally until
DCUCR.WEAK_SPCA
is set to 0. To wait for completion of the cache flush, a
member #Sync
must be issued after
DCUCR.WEAK_SPCA
is set to 0.
Executing a
membar #Sync
while the
DCUCR.WEAK_SPCA
= 1 after writing 1
to
ASI_L2_CTRL.U2_FLUSH
does not wait for the cache flush to complete.
40:33
PM
<7:0>
Defined in SPARC JPS1 Commonality.
32:25
VM
<7:0>
Defined in SPARC JPS1 Commonality.
24, 23
PR
,
PW
Defined in SPARC JPS1 Commonality.
22, 21
VR
,
VW
Defined in SPARC JPS1 Commonality.
20:4
—
Reserved.
3
DM
Defined in SPARC JPS1 Commonality.
2
IM
Defined in SPARC JPS1 Commonality.
Implementation dependent
PM
VM
PR
PW
VR
DM
0
0
1
2
3
4
21
22
23
40
42
20
VW
24
25
32
33
47
IM
0
0
48
49
0
50
63
—
—
WEAK_SPCA
41
Summary of Contents for SPARC JPS1
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Page 26: ...15 F CHAPTER 4 Data Formats Please refer to Chapter 4 Data Formats in Commonality ...
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Page 118: ...F APPENDIX 107 G Assembly Language Syntax Please refer to Appendix G of Commonality ...
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Page 120: ...F APPENDIX 109 H Software Considerations Please refer to Appendix H of Commonality ...
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Page 124: ...F APPENDIX 113 J Changes from SPARC V8 to SPARC V9 Please refer to Appendix K of Commonality ...
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Page 126: ...F APPENDIX 115 K Programming with the Memory Models Please refer to Appendix J of Commonality ...
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Page 234: ...223 F CHAPTER Bibliography General References Please refer to Bibliography in Commonality ...
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