What are the measures to be taken to design for optimized area?

Measures to design for optimized area (minimum silicon) using architecture/RTL, synthesis, and floorplanning levers.

Area Optimization

Why area matters: As silicon real-estate is very costly and saving is directly proportional to the company's revenue generation, a lot of emphasis is placed on designing which has optimal utilization in the area-front.

1) Architecture-level (biggest impact)

• Resource sharing / time-multiplexing: reuse ALU/multiplier across cycles instead of duplicating blocks.
• Reduce parallelism when throughput allows.
• Bit-width optimization: use only required word length (trim unused bits).
• Use memory macros: replace large flop arrays with SRAM/ROM whenever feasible.
• Simpler arithmetic: shift/add vs multiply if allowed by spec.

2) RTL / micro-architecture

• Remove redundant logic: share common sub-expressions and decodes.
• Avoid unnecessary pipelining: extra registers increase area (and clock overhead).
• FSM encoding (ASIC): binary/compact encodings typically use fewer flops than one-hot.
• Control mux growth: restructure to avoid very wide mux trees.

3) Synthesis-driven techniques

• Don’t over-constrain timing: aggressive constraints lead to upsizing/buffering → more area.
• Use low-drive cells on non-critical paths: if the path is not timing-critical, optimize the cells to use low-drive strength cells so that there will be saving in the area.
• Enable area-focused compile (tool option) and/or apply set_max_area targets.
• Manage fanout early: high fanout nets often cause buffer insertion (area increase).

Quick win: Move non-critical logic to minimum-size / low-drive cells and relax timing where legally possible.

4) Floorplanning / physical (ASIC)

• Abut the VDD rows (clean standard-cell row strategy) to improve utilization and reduce wasted whitespace.
• Iterate floorplans: analyzing utilization numbers with multiple floor-planning versions which brings up with optimized area targets.
• Reduce congestion (better macro placement/channel sizing) to avoid late buffering and detours.

Example (typical synthesis knobs)

/* Generic (tool-dependent) examples */
# Set an area target (units depend on library)
set_max_area 0

# Use an area-focused compile (name varies by tool)
compile -area_effort high

# Ensure non-critical paths are allowed to use smaller cells
# (avoid over-aggressive timing constraints)

Best practice: optimize architecture first, then let synthesis pick smaller cells on non-critical paths, and validate with floorplan utilization.

Architecture • Synthesis • Floorplan