• The data from the input fifo is processed to find destination router
• The sender router waits for the destination router's token (Semaphore)
• When the semaphore is available, the sender writes the data using non-blocking write to destination router's output fifo - this confirms whether space available in the fifo too
Corona is a 3D many-core architecture with 256 low-power multithreaded cores, organized into 64 clusters with each cluster having 4 cores and hub to facilitate communication. It uses nanophotonic communication for both inter-core and off-stack communication to memory or I/O devices. Each cluster has a channel associated with it. The channel starts at a cluster and passes through all other clusters and ends at the home cluster in a serpentine manner. Only the home cluster can read from the channel, but all other clusters can write into the channel. Each cluster has a token associated with it. The clusters can write into the channels of any other cluster by acquiring destination cluster’s token.
The key components include:
• A photonic crossbar that fully interconnects the cores
Communication in Corona is controlled through a distributed, all-optical, token-based arbitration scheme. This means:
• Each node participates in the token management process
• Optical tokens circulate continuously through the network
• Nodes must acquire a token to gain access to a communication channel
3. Communication Decisions:
The decision-making process for communication is as follows:
• When to communicate: A node initiates communication when it has data to send and has acquired the appropriate token.
• Who to communicate with: The destination is determined by the application needs. The photonic crossbar allows any node to communicate with any other node.
• When to stop: After completing its transmission, the node releases the token back into the network.
4. Broadcast bus
• In addition, there is a broadcast bus waveguide, to which all clusters can read and write
• The clusters can write a common message into the broadcast bus by acquiring the broadcast token.
The corona architecture has a global optical clock and the local optical clock is in phase synchronization with the global clock.
In general, if we consider any particular cluster ‘n’, there will be a number of activities going on;
• Detecting token to transmit data
• Divert and acquire the token when it is detected
• Transmit data by modulating light on the desired channel
• Release the token once the data transmission is finished
• Detect broadcast token when it has a broadcast message to send
• Divert and acquire the broadcast token when it is detected
• Send broadcast message by modulating light on the broadcast channel
• Release broadcast token when broadcast message transmission is finished
• Detects for messages on home channel ‘n’ (Reading data)
• Detecting the broadcast channel for broadcast messages
