Structural Hazards

Structural Hazard: a possible interruption to a computation or flow of data owing to a physical resource that has insufficient capacity. Consequently, operations that could potentially be done in parallel have to be done serially.

Examples:

• insufficient number ALUs for all of the operations to be schedulled in current clock tick.
• insufficient number of ports on a RAM/register file.

A Non-fully pipelined component: is unable to start a new operation on every clock cycle.

Such a component:

• has a start input and a busy/ready output
• and will go busy for a constant or variable number of cycles.

Example: fixed point multipliers and dividers (see additional material).

Example: all floating point operations tend to be implemented with multi-cycle units.