Technical data

VAX 6000 Series Vector Processor
2.9 VECTOR PIPELINING
The vector processor, which is fully pipelined, has three major function
units: the vector issue unit, the load/store unit, and the arithmetic unit
(see Figure 2–10). These function units operate independently and are
fully pipelined. Vector instructions are received by the issue unit from
the scalar processor. The issue unit decodes the instruction, performs
various checks, and issues the instruction to either the load/store unit
or the arithmetic unit. At that point, the issue unit is finished with that
instruction and control of the instruction passes to the function unit to
which it was issued.
Figure 2–10 Vector Processor Units
Arithmetic
Unit
msb-0584-90
Load/Store
Unit
Vector
Issue
Unit
2.9.1 Vector Issue Unit
The vector issue unit acts as the controller for the vector pipeline. It
handles vector instruction decomposition, resource availability checks,
and vector instruction issue.
When an instruction is received by the vector module from the scalar
processor, the instruction is decomposed into its opcode and operands,
and the availability of the requested resources is checked. All source
and destination registers must be available before instruction execution
begins. The function unit to be used by the instruction during execution
must also be available. The instruction is not issued until all required
resources are available.
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