HP Vectra XW Optimization Manual page 26

Why 16-bit Applications
are Slower
Next instruction
waiting to enter
the pipeline
NOTE
1 Your Personal Workstation's Performance Features
Benefits of 32-bit Applications
When executing 16-bit instructions, the Pentium Pro processor is
limited by two constraints. First, the Pentium Pro cannot mix 32-bit and
16-bit instructions in a pipeline. Second, at any moment only one 16-bit
instruction can normally be present in a pipeline.
When running a 16-bit application, all instructions are 16-bits and so
each instruction is executed singly, without use of the pipeline's
queuing facility. In effect, the pipeline is not used. Since the pipeline is
the processor's most important means of accelerating instruction
execution, the negative impact on performance is significant.
Processor pipeline
Instruction
execution steps
For the reasons explained above, HP does not recommend using your
Personal Workstation to run 16-bit applications. Best performance can
only be obtained when running 32-bit applications.
20 English
Only one 16-bit instruction can be in the pipeline at once