US Patent No. 9,280,503

ROUND ROBIN ARBITER HANDLING SLOW TRANSACTION SOURCES AND PREVENTING BLOCK


Patent No. 9,280,503
Issue Date March 08, 2016
Title Round Robin Arbiter Handling Slow Transaction Sources And Preventing Block
Inventorship Gurjeet S. Saund, Saratoga, CA (US)
Deniz Balkan, Santa Clara, CA (US)
Munetoshi Fukami, Newark, CA (US)
Assignee Apple Inc., Cupertino, CA (US)

Claim of US Patent No. 9,280,503

1. An apparatus comprising:
a plurality of transaction sources; and
a fabric interface circuit coupled to the plurality of transaction sources, wherein a first transaction rate corresponding
to a first transaction source of the plurality of transaction sources is limited compared to a second transaction rate of
at least one other transaction source of a plurality of transaction sources, and wherein the fabric interface circuit includes
an arbiter configured to arbitrate among transactions from the plurality of sources using a deficit-weighted arbitration scheme,
and wherein the first transaction rate is limited by one or more attributes of the first transaction source independent of
the deficit-weighted arbitration scheme, and wherein the arbiter is configured to delay a reload of deficit weights responsive
to receiving a lack of a transaction from the first transaction source and the first transaction source has unconsumed weight,
wherein the delay is dependent on a ratio of the second transaction rate to the first transaction rate, and wherein the arbiter
is configured to reload the deficit weights at an expiration of the delay in response to not receiving a subsequent transaction
from the first transaction source during the delay, and wherein the arbiter is configured to reload the deficit weights at
the expiration of the delay even in a case that the first transaction source has unconsumed weight at the expiration of the
delay.