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Method and Apparatus for a Programmable Per Requestor Weighted 2-Level Round Robin Arbiter

IP.com Disclosure Number: IPCOM000022282D
Original Publication Date: 2004-Mar-04
Included in the Prior Art Database: 2004-Mar-04
Document File: 1 page(s) / 42K

Publishing Venue

IBM

Abstract

This is a programmable weighted arbitration scheme. It will allow for the availability of multiple resources in the selection of the arbitration winner and will not allow starvation of any requestor. This is well suited to maximize bandwidth into a memory subsystem or multi-bank DRAM unit.

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Method and Apparatus for a Programmable Per Requestor Weighted 2-Level Round Robin Arbiter

How to access memory for many requestors with some requestors needing more memory accesses than other requestors, but also ensuring that no requestor gets starved from memory accesses for an extended period of time. Also takes into account memory bank status, so that the DRAM controller is always presented a request to a free bank rather than waste memory bandwidth by giving a request to a busy bank.

     This invention utilizes two round robin priority wheels. Each requestor starts off on the low wheel and are chosen in a round robin fashion. Each requestor also has a certain number of winners (each cycle that a valid winner is chosen) that can be chosen before that requestor jumps to the high priority wheel. Requestors are chosen off the high priority wheel in round-robin fashion. Obviously, any requestors on the high wheel are chosen before any requestors on the low wheel. We also took into account which bank each requestor wanted to read/write from. Memory accesses should always be made to free banks to maximize DRAM bandwidth utilization. If the winner from the high round robin wheel was going to a busy bank, then the next requestor on the high wheel would be chosen, if they were going to a free memory bank. Once you are chosen as a winner from the high wheel, your counter (number of cycles you have waited) is reset, which causes that requestor to fall back down to the low...