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Dual Data Checking With Masked Data Fetch and Modify Device

IP.com Disclosure Number: IPCOM000039496D
Original Publication Date: 1987-Jun-01
Included in the Prior Art Database: 2005-Feb-01
Document File: 2 page(s) / 37K

Publishing Venue

IBM

Related People

Jacobs, MN: AUTHOR [+2]

Abstract

The ability to check data in a masked data fetch and modifying device is provided when the modifying data type is different from that of the fetched data. In a masked data fetch and modifying device, loading of fetch data is inhibited by a mask bit where modify data is placed. The mask bit is also used to identify the type of data. In the figure, when a masked data fetch with a modifying device is used in a computer system, the data contained in the register under consideration may contain modifying data, fetched data, or both data types. The modifying data may originate from an internal path in the CPU and will usually contain parity. The fetch data may originate from an external memory device and will usually contain a corresponding error correction code (ECC) bit.

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Dual Data Checking With Masked Data Fetch and Modify Device

The ability to check data in a masked data fetch and modifying device is provided when the modifying data type is different from that of the fetched data. In a masked data fetch and modifying device, loading of fetch data is inhibited by a mask bit where modify data is placed. The mask bit is also used to identify the type of data. In the figure, when a masked data fetch with a modifying device is used in a computer system, the data contained in the register under consideration may contain modifying data, fetched data, or both data types. The modifying data may originate from an internal path in the CPU and will usually contain parity. The fetch data may originate from an external memory device and will usually contain a corresponding error correction code (ECC) bit. In any portion of the register under consideration Data Byte(w) 100 with an error checking bit described by Pw 101 (one byte will suffice for this discussion), the Mask(w) bit 105 will indicate if the fetch data should be loaded upon completion of a fetch or if the loading of fetch data should be inhibited. Additionally, the Mask(w) 105 will also indicate the origin of the data. In the Data Check Selector 104, if the Mask(w) bit 105 is OFF and the fetch associated with the register means under consideration 100 is not pending as indicated by Fetch Pending 106 being OFF is true, then the fetch has completed, and no modification of the byte 10...