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A method to route and discard data sent from a memory source.

IP.com Disclosure Number: IPCOM000013772D
Original Publication Date: 2000-Oct-01
Included in the Prior Art Database: 2003-Jun-18
Document File: 1 page(s) / 38K

Publishing Venue

IBM

Abstract

Disclosed is a mechanism to prevent data, which might have been sourced by a memory device in response to a Read request from a master device, from reaching the issuing master, in case, in the mean time, the Read request gets aborted by it. The solution described here assumes a node controller (NC) or router based environment, but could be adapted to other types. Certain read transactions requested by a processor and held in a NC may be aborted by the processor after memory has committed to sending the data. For example: 1. a Read transaction from the processor is accepted by the NC 2. the NC will instruct the processor to re-issue the command at a later time

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A method to route and discard data sent from a memory source.

Disclosed is a mechanism to prevent data, which might have been sourced by a memory device in response to a Read request from a master device, from reaching the issuing master, in case, in the mean time, the Read request gets aborted by it. The solution described here assumes a node controller (NC) or router based environment, but could be adapted to other types.

Certain read transactions requested by a processor and held in a NC may be aborted by the processor after memory has committed to sending the data. For example:

1. a Read transaction from the processor is accepted by the NC
2. the NC will instruct the processor to re-issue the command at a later time
3. meanwhile, the NC will forward the command for global snoop
4. after the global coherence has been performed, the memory controller will forward the data to the NC
5. the processor will re-issue the command, but abort the command in its local window
6. it is the NC's responsibility to not forward this data to the processor and should subsequently discard it. The processor at this point is not expecting to see any data for this transaction.

The data corresponding to a load/store transaction is tracked using a data tag that matches the tag associated with the address portion of the transaction. After an abort condition like the one described above, the processor may reuse the aborted tag to start a new transaction. Data corruption can occur if the da...