1:24
Volume 1, Part 1: Execution Environment
ignore the value written. In variable-sized register sets, registers which are
unimplemented in a particular processor are also reserved registers. An access to one
of these unimplemented registers causes a Reserved Register/Field fault.
Within defined registers, fields which are not defined are either reserved or ignored. For
reserved fields
, hardware will always return a zero on a read. Software must always
write zeros to these fields. Any attempt to write a non-zero value into a reserved field
will raise a Reserved Register/Field fault.
Reserved
fields may have a possible future
use.
For
ignored fields
, hardware will return a 0 on a read, unless noted otherwise.
Software may write any value to these fields since the hardware will ignore any value
written. Except where noted otherwise some IA-32 ignored fields may have a possible
future use.
summarizes how the processor treats reserved and ignored registers and
fields.
For defined fields in registers, values which are not defined are reserved. Software
must always write defined values to these fields. Any attempt to write a
reserved
value
will raise a Reserved Register/Field fault. Certain registers are
read-only
registers
. A write to a read-only register raises an Illegal Operation fault.
When fields are marked as
reserved
, it is essential for compatibility with future
processors that software treat these fields as having a future, though unknown effect.
Software should follow these guidelines when dealing with
reserved
fields:
• Do not depend on the state of any reserved fields. Mask all reserved fields before
testing.
• Do not depend on the state of any reserved fields when storing to memory or a
register.
• Do not depend on the ability to retain information written into reserved or ignored
fields.
• Where possible reload reserved or ignored fields with values previously returned
from the same register, otherwise load zeros.
Table 3-1.
Reserved and Ignored Registers and Fields
Type
Read
Write
Reserved register
Illegal Operation fault
Illegal Operation fault
Ignored register
0
Value written is discarded
Reserved field
0
Write of non-zero causes Reserved Reg/Field fault
Ignored field
0 (unless noted otherwise)
Value written is discarded
Summary of Contents for ITANIUM ARCHITECTURE - SOFTWARE DEVELOPERS VOLUME 3 REV 2.3
Page 1: ......
Page 11: ...x Intel Itanium Architecture Software Developer s Manual Rev 2 3 ...
Page 13: ...1 2 Intel Itanium Architecture Software Developer s Manual Rev 2 3 ...
Page 33: ...1 22 Volume 1 Part 1 Introduction to the Intel Itanium Architecture ...
Page 57: ...1 46 Volume 1 Part 1 Execution Environment ...
Page 147: ...1 136 Intel Itanium Architecture Software Developer s Manual Rev 2 3 ...
Page 149: ...1 138 Volume 1 Part 2 About the Optimization Guide ...
Page 191: ...1 180 Volume 1 Part 2 Predication Control Flow and Instruction Stream ...
Page 230: ......
Page 248: ...236 Intel Itanium Architecture Software Developer s Manual Rev 2 3 ...
Page 250: ...2 2 Intel Itanium Architecture Software Developer s Manual Rev 2 3 ...
Page 264: ...2 16 Volume 2 Part 1 Intel Itanium System Environment ...
Page 380: ...2 132 Volume 2 Part 1 Interruptions ...
Page 398: ...2 150 Volume 2 Part 1 Register Stack Engine ...
Page 486: ...2 238 Volume 2 Part 1 IA 32 Interruption Vector Descriptions ...
Page 750: ...2 502 Intel Itanium Architecture Software Developer s Manual Rev 2 3 ...
Page 754: ...2 506 Volume 2 Part 2 About the System Programmer s Guide ...
Page 796: ...2 548 Volume 2 Part 2 Interruptions and Serialization ...
Page 808: ...2 560 Volume 2 Part 2 Context Management ...
Page 842: ...2 594 Volume 2 Part 2 Floating point System Software ...
Page 850: ...2 602 Volume 2 Part 2 IA 32 Application Support ...
Page 862: ...2 614 Volume 2 Part 2 External Interrupt Architecture ...
Page 870: ...2 622 Volume 2 Part 2 Performance Monitoring Support ...
Page 891: ......
Page 1099: ...3 200 Volume 3 Instruction Reference padd Interruptions Illegal Operation fault ...
Page 1295: ...3 396 Volume 3 Resource and Dependency Semantics ...
Page 1296: ......
Page 1302: ...402 Intel Itanium Architecture Software Developer s Manual Rev 2 3 ...
Page 1494: ...4 192 Volume 4 Base IA 32 Instruction Reference FWAIT Wait See entry for WAIT ...
Page 1647: ...Volume 4 Base IA 32 Instruction Reference 4 345 ROL ROR Rotate See entry for RCL RCR ROL ROR ...
Page 1884: ...4 582 Volume 4 IA 32 SSE Instruction Reference ...
Page 1885: ...Index Intel Itanium Architecture Software Developer s Manual Rev 2 3 Index ...
Page 1886: ...Index Intel Itanium Architecture Software Developer s Manual Rev 2 3 ...
Page 1898: ...INDEX Index 12 Index for Volumes 1 2 3 and 4 ...