Compaq ECQD2KCTE manual Must Be Zero MBZ, Read As Zero RAZ, Should Be Zero SBZ, Ignore IGN

Models: ECQD2KCTE

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1.6.6 Must Be Zero (MBZ)

Fields specified as Must be Zero (MBZ) must never be filled by software with a non-zero value. These fields may be used at some future time. If the processor encounters a non-zero value in a field specified as MBZ, an Illegal Operand exception occurs.

1.6.7 Read As Zero (RAZ)

Fields specified as Read as Zero (RAZ) return a zero when read.

1.6.8 Should Be Zero (SBZ)

Fields specified as Should be Zero (SBZ) should be filled by software with a zero value. Non- zero values in SBZ fields produce UNPREDICTABLE results and may produce extraneous instruction-issue delays.

1.6.9 Ignore (IGN)

Fields specified as Ignore (IGN) are ignored when written.

1.6.10 Implementation Dependent (IMP)

Fields specified as Implementation Dependent (IMP) may be used for implementation-specific purposes. Each implementation must document fully the behavior of all fields marked as IMP by the Alpha specification.

1.6.11 Illustration Conventions

Illustrations that depict registers or memory follow the convention that increasing addresses run right to left and top to bottom.

1.6.12 Macro Code Example Conventions

All instructions in macro code examples are either listed in Chapter 4 or are stylized code forms found in Section A.4.6.

Introduction 1–9

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Compaq ECQD2KCTE manual Must Be Zero MBZ, Read As Zero RAZ, Should Be Zero SBZ, Ignore IGN, Implementation Dependent IMP