Reconfigurable Buffered Interconnect for Latency and Energy Optimization
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Solution Overview
Problem
Current processor designs face challenges in operating efficiently across a wide range of supply voltages and power modes, leading to sub-optimal performance and energy consumption due to limitations in resistive interconnects, which are exacerbated by technology scaling.
Innovation Solution
A reconfigurable interconnect system that dynamically adjusts between bandwidth, latency, and energy modes by controlling pairs of buffered interconnect links, allowing for on-the-fly tuning of latency, bandwidth, and energy consumption without additional wiring or complex circuitry, using arbiter circuits and a power management unit to adapt to workload needs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If buffered interconnects are used to connect MESH-stops or RING-stops, then signal transmission can be achieved, but latency, bandwidth and energy consumption are limited by long repeated/buffered wires spanning several millimeters
Solution Approach 1:
The interconnect is divided into multiple segments with repeaters placed at optimized intervals. Each segment is independently optimized for signal integrity, allowing the overall interconnect to span longer distances without degradation while maintaining timing performance through distributed buffering.
Solution Approach 2:
Repeaters act as intermediary elements between source and destination, regenerating and re-timing signals at intermediate points. This mediation allows signals to traverse longer physical distances without direct end-to-end timing constraints, effectively decoupling physical length from logical latency.
2Use of energy by moving object
If a single product design operates at different supply voltages, then power envelope requirements can be met, but performance is compromised due to sub-optimal interconnect design for each voltage range
Solution Approach 1:
The interconnect design dynamically adjusts repeater buffering and signal timing based on operating voltage and frequency. At higher voltages/frequencies, enhanced buffering and re-timing are activated to maintain signal integrity, while at lower voltages, the design operates with reduced overhead, optimizing power-performance across the full operating range.
Solution Approach 2:
The system changes interconnect parameters such as repeater density, buffer size, and signal timing based on operating conditions. By adjusting these parameters according to voltage and frequency settings, the interconnect maintains optimal performance across different power modes without requiring separate designs for each operating point.
3Productivity
If inter-repeater distances, buffer sizes, wire layer, wire widths and wire spacing are optimized, then interconnect performance can be improved, but design complexity increases
Solution Approach 1:
The repeater design serves multiple functions simultaneously: signal regeneration, timing adjustment, and voltage level translation. This multi-functionality allows a single standardized repeater cell to be used across different interconnect scenarios, reducing design complexity while maintaining optimized performance through parameter adjustment rather than structural variation.
4Quantity of substance
If technology scaling is applied, then transistor density increases, but interconnect resistance increases further exacerbating the challenge
Solution Approach 1:
The design replaces purely resistive interconnect models with active buffered interconnects that use transistors to regenerate signals. This substitution of passive electrical transmission with active signal regeneration overcomes the increased resistance effects from technology scaling, allowing continued density improvement without proportional performance degradation.
Data Source
AI summary
Described is an low overhead method and apparatus to reconfigure a pair of buffered interconnect links to operate in one of these three modes—first mode (e.g., bandwidth mode), second mode (e.g., latency mode), and third mode (e.g., energy mode). In bandwidth mode, each link in the pair buffered interconnect links carries a unique signal from source to destination. In latency mode, both links in the pair carry the same signal from source to destination, where one link in the pair is “primary” and other is called the “assist”. Temporal alignment of transitions in this pair of buffered interconnects reduces the effective capacitance of primary, thereby reducing delay or latency. In energy mode, one link in the pair, the primary, alone carries a signal, while the other link in the pair is idle. An idle neighbor on one side reduces energy consumption of the primary.