authors: Jason Lowe-Power
last edited: 2023-01-11 16:05:55 +0000

Garnet Standalone

This is a dummy cache coherence protocol that is used to operate Garnet in a standalone manner. This protocol works in conjunction with the Garnet Synthetic Traffic injector.

Cache Hierarchy

This protocol assumes a 1-level cache hierarchy. The role of the cache is to simply send messages from the cpu to the appropriate directory (based on the address), in the appropriate virtual network (based on the message type). It does not track any state. Infact, no CacheMemory is created unlike other protocols. The directory receives the messages from the caches, but does not send any back. The goal of this protocol is to enable simulation/testing of just the interconnection network.

Stable States and Invariants

States Invariants
I Default state of all cache blocks

Cache controller

The network tester (in src/cpu/testers/networktest/ generates packets of the type ReadReq, INST_FETCH, and WriteReq, which are converted into RubyRequestType:LD, RubyRequestType:IFETCH, and RubyRequestType:ST, respectively, by the RubyPort (in src/mem/ruby/system/RubyPort.hh/cc). These messages reach the cache controller via the Sequencer. The destination for these messages is determined by the traffic type, and embedded in the address. More details can be found here.

Directory controller

Other features

This protocol assumes only 3 vnets.