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Release 1.0, 1 July 2002 F. Chapter 5 Registers 21
The Performance Control Register in SPARC64 V is illustrated in
FIGURE 5-1
and
described in
TABLE 5-2
.
FIGURE 5-1
SPARC64 V Performance Control Register (PCR) (ASR 16)
TABLE 5-2
PCR
Bit Description
Bit Field Description
47:32 OVF Overflow Clear/Set/Status. Used to read counter overflow status (via RDPCR) and clear
or set counter overflow status bits (via WRPCR). PCR.OVF is a SPARC64 V-specific field
(impl. dep. #207).
The following figure depicts the bit layout of SPARC64 V OVF field for four counter
pairs. Counter status bits are cleared on write of 0 to the appropriate OVF bit.
26 OVRO Overflow read-only. Write-only/read-as-zero field specifying PCR.OVF update behavior
for WRPCR.PCR. The OVRO field is implementation -dependent (impl. dep. #207).
WRPCR.PCR with PCR.OVRO = 1 inhibits updating of PCR.OVF for the current write
only. The intention of PCR.OVRO is to write PCR while preserving current PCR.OVF
value. PCR.OVF is maintained internally by hardware, so a subsequent RDPCR.PCR
returns accurate overflow status at the time.
24:22 NC Number of counter pairs. Three-bit, read-only field specifying the number of counter
pairs, encoded as 0–7 for 1–8 counter pairs (impl. dep. #207).
For SPARC64 V, the hardcoded value of NC is 3 (indicating presence of 4 counter pairs).
20:18 SC Select PIC. In SPARC64 V, three-bit field specifying which counter pair is currently
selected as PIC (ASR 17) and which SU/SL values are visible to software. On write,
PCR.SC selects which counter pair is updated (unless PCR.ULRO is set; see below). On
read, PCR.SC selects which counter pair is to be read through PIC (ASR 17).
16:11 SU Defined (as S1) in SPARC JPS1 Commonality.
9:4 SL Defined (as S0) in SPARC JPS1 Commonality.
3 ULRO Implementation-dependent field (impl. dep. #207) that specifies whether SU/SL are
read-only. In SPARC64 V, this field is write-only/read-as-zero, specifying update
behavior of SU/SL on write. When PCR.ULRO = 1, SU/SL are considered as read-only;
the values set on PCR.SU/PCR.SL are not written into SU/SL. When PCR.ULRO = 0,
SU/SL are updated. PCR.ULRO is intended to switch visible PIC by writing PCR.SC,
without affecting current selection of SU/SL of that PIC. On PCR read, PCR.SU/PCR.SL
always shows the current setting of the PIC regardless of PCR.ULRO.
2 UT Defined in SPARC JPS1 Commonality.
1 ST Defined in SPARC JPS1 Commonality.
63 16 10
9
40
OVF 0 SLSU0SC
1718
21
0
NC
2224
0OVRO
26273132
0
4748
0
25
ULRO UT ST PRIV
12311
20
15
L0U0L1U10
01234567
L2U2L3U3