Shared GPU Control Bus for Cross-Substrate Workload Distribution
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Solution Overview
Problem
Existing graphics processors face challenges in efficiently distributing graphics workloads across multiple replicated GPU sub-units due to limitations in control bus architectures, leading to inefficiencies in scalability and resource utilization.
Innovation Solution
A shared control bus architecture that provides point-to-point communication between global and distributed clients, enabling efficient workload distribution and scalability across various numbers of GPU sub-units, with features like arbitration, priority-based packet handling, and asynchronous/synchronous connections.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a shared control bus architecture is implemented to distribute workloads across multiple GPU sub-units, then scalability and resource utilization are improved, but control signal routing complexity and arbitration overhead increase
Solution Approach 1:
The control bus is segmented into multiple independent lanes that can be selectively activated. Each lane can be assigned to specific GPU sub-units, allowing the system to scale by adding lanes rather than increasing the complexity of existing routing paths. This segmentation enables linear scalability while keeping individual lane complexity manageable.
Solution Approach 2:
The control bus employs dynamic lane assignment and switching mechanisms that allow flexible reconfiguration of control signal routing based on workload distribution requirements. The system can dynamically allocate lanes to different GPU sub-units, providing adaptability without requiring static complex routing designs for all possible configurations.
2Productivity
If multiple lanes are added to the control bus to support more GPU sub-units, then bandwidth and throughput are improved, but signal integrity and timing synchronization become more difficult to maintain
Solution Approach 1:
The control bus is divided into multiple independent lanes, each capable of carrying control signals separately. This segmentation allows parallel transmission of control signals to different GPU sub-units, increasing overall bandwidth while maintaining signal integrity on each individual lane through standard single-lane timing protocols.
Solution Approach 2:
The system implements lane activation based on actual workload requirements rather than requiring all lanes to be active simultaneously. This partial action approach allows the system to maintain signal integrity by activating only the necessary number of lanes for current operations, avoiding the timing synchronization challenges of fully utilizing all lanes under all conditions.
3Ease of operation
If arbitration mechanisms are implemented to manage control signal access, then fair bandwidth utilization is improved, but latency and control signal processing time increase
Solution Approach 1:
The arbitration mechanism dynamically adjusts lane assignment based on real-time workload distribution and GPU sub-unit readiness states. This dynamic approach enables fair bandwidth allocation by assigning lanes to sub-units that are ready to receive control signals, minimizing unnecessary waiting time and reducing overall latency while maintaining fairness.
Solution Approach 2:
The control bus incorporates feedback mechanisms where GPU sub-units signal their readiness and completion status. This feedback information is used by the arbitration logic to make informed decisions about lane assignment, allowing fair bandwidth utilization while minimizing latency by avoiding assignment to unavailable sub-units and prioritizing sub-units that are ready to process control signals immediately.
Data Source
AI summary
Techniques are disclosed relating to a shared control bus for communicating between primary control circuitry and multiple distributed graphics processor units. In some embodiments, a set of multiple graphics processor units including at least first and second graphics processors on different semiconductor substrates that are packaged in a multi-chip module, where the first and second graphics processors are coupled to access graphics data via respective memory interfaces. The shared workload distribution bus may include: one or more interfaces between respective graphics processors on the same semiconductor substrate and at least one cross-substrate interface between the different semiconductor substrates. Workload distribution circuitry may transmit, via the shared workload distribution bus, control data that specifies graphics work distribution to the multiple graphics processor units. Packet control circuitry may modify packets from at least one of the one or more interfaces for transmission via the cross-substrate interface.