FMA Unit Power Reduction via Input-Driven Clock Gating
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Solution Overview
Problem
Current FMA unit designs in processors consume excessive power due to their constant operation, regardless of data inputs, and previous solutions to reduce power consumption are either expensive in terms of area and leakage power or ineffective in saving power during FMA instruction execution.
Innovation Solution
Implementing data input-driven fine-grain clock gating and bypass paths within the FMA unit to power down unnecessary components based on the analysis of input data values and instruction types, allowing for efficient operation by bypassing or gating off power-hungry units during simpler operations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If the FMA unit operates at full power for all operations, then computational accuracy and speed are maintained, but power consumption becomes excessive
Solution Approach 1:
The patent implements dynamic power management by making the FMA unit's operational state dependent on input data characteristics. Clock gating mechanisms dynamically enable or disable portions of the multiplier based on whether inputs are zero or non-zero, transforming a static power consumption model into a dynamic one that adapts to computational needs.
Solution Approach 2:
The patent applies local quality by selectively powering down specific portions of the FMA unit (particularly the multiplier) based on local input conditions. When one input is zero, only the corresponding multiplier portion is disabled, while other portions remain active, allowing localized power savings without compromising overall computational functionality.
2Use of energy by moving object
If a separate floating point ALU is added to handle simpler operations, then power consumption for simple operations is reduced, but area and leakage power increase
Solution Approach 1:
The patent makes the existing FMA unit multi-functional by enabling it to handle both complex FMA operations and simpler operations (addition, subtraction, multiplication) using the same hardware resources. By selecting appropriate input values (e.g., setting one input to zero for multiplication), the unit performs different functions without requiring separate dedicated circuits, thus avoiding area increases.
Solution Approach 2:
The patent merges multiple operation types into a single FMA unit by using operand selection and clock gating strategies. Instead of having separate ALUs for different operations, the design combines addition, subtraction, multiplication, and FMA capabilities into one unified unit that adapts its behavior based on input characteristics and control signals.
3Use of energy by moving object
If clock gating is implemented to power down components, then power consumption is reduced, but control complexity increases
Solution Approach 1:
The patent implements preliminary action by analyzing input data characteristics before enabling or disabling clock gating. The control logic examines input operands in advance to determine which portions of the multiplier should be powered down, allowing proactive power management rather than reactive control, which simplifies the overall control architecture.
4Use of energy by moving object
If the FMA unit is optimized for power savings during simple operations, then average power consumption decreases, but power savings during FMA instruction execution are lost
Solution Approach 1:
The patent implements dynamic power management by making the FMA unit's operational state dependent on input data characteristics. Clock gating mechanisms dynamically enable or disable portions of the multiplier based on whether inputs are zero or non-zero, transforming a static power consumption model into a dynamic one that adapts to computational needs.
Data Source
AI summary
In an embodiment, a fused multiply-add (FMA) circuit is configured to receive a plurality of input data values to perform an FMA instruction on the input data values. The circuit includes a multiplier unit and an adder unit coupled to an output of the multiplier unit, and a control logic to receive the input data values and to reduce switching activity and thus reduce power consumption of one or more components of the circuit based on a value of one or more of the input data values. Other embodiments are described and claimed.