Which of the following is/are part of an Instruction Set Architecture of a processor?

An Instruction Set Architecture (ISA) defines the programmer-visible interface of the processor, which includes:

• The instruction set (operations, opcodes, formats)

• Addressing modes and data types

• The programmer-visible register file, including the total number of architectural registers

• Memory addressing and byte ordering

In contrast, microarchitectural and hardware implementation details include:

• Size of cache memory (Option A)

• Processor clock frequency (Option B)

• Number of cache memory levels (Option C)

These microarchitectural features are transparent to the ISA. Therefore, only D is part of the ISA.