Sun Microelectronics
42
UltraSPARC User’s Manual
VA_tag<63:22>
: Virtual Address Tag. The virtual page number. Bits 21 through 13
are not maintained in the tag, since these bits are used to index the
smallest direct-mapped TSB of 64 entries.
Note:
Software must sign-extend bits VA_tag<63:44> to form an in-range VA.
V
:
Valid: If the Valid bit is set, the remaining fields of the TTE are
meaningful. Note that the explicit Valid bit is redundant with the
software convention of encoding an invalid TTE with an unused context.
The encoding of the context field is necessary to cause a failure in the TTE
tag comparison, while the explicit Valid bit in the TTE data simplifies the
TLB miss handler.
Size
:
The page size of this entry, encoded as shown in the following table.
NFO
:
No-Fault-Only. If this bit is set, loads with
ASI_PRIMARY_NO_FAULT{_LITTLE},
ASI_SECONDARY_NO_FAULT{_LITTLE} are translated. Any other
access will trap with a
data_access_exception
trap (FT=10
16
). The NFO-bit
in the I-MMU is read as zero and ignored when written. If this bit is set
before loading the TTE into the TLB, the iTLB miss handler should
generate an error.
IE
:
Invert Endianness. If this bit is set, accesses to the associated page are
processed with inverse endianness from what is specified by the
instruction (big-for-little and little-for-big). See Section 6.6, “ASI Value,
Context, and Endianness Selection for Translation,” on page 52 for
details. In the I-MMU this bit is read as zero and ignored when written.
Note:
This bit is intended to be set primarily for noncacheable accesses. The
performance of cacheable accesses will be degraded as if the access had missed
the D-Cache.
Table 6-1
Size Field Encoding (from TTE)
Size<1:0>
Page Size
00
8 Kb
01
64 Kb
10
512 Kb
11
4 Mb
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