pub const NOC_MAX_BURST_BYTES: u64 = 8192;Expand description
The largest payload one NOC command carries. A transfer longer than this is split by
ncrisc_noc_fast_write_any_len into burst-sized commands, each of which the network interface
issues — and counts — separately.
★ THIS IS WHY A MULTICAST IS NOT ONE TRANSACTION. It is one COMMAND per burst, and a multicast page
is usually far larger than a burst: a 4x10 tile page is 81,920 bytes, which is ten of them. Modelling
a multicast as a single transaction under-counted the busiest plans by 10%, and the term was found by
reading ncrisc_noc_fast_write_any_len rather than by fitting anything.
Wormhole: NOC_MAX_BURST_WORDS (256) * NOC_WORD_BYTES (32), from tt-metal’s
wormhole/noc/noc_parameters.h. It belongs on the target descriptor the day a chip disagrees.