Browse Prior Art Database

Early Address Decode on a Partial Address

IP.com Disclosure Number: IPCOM000036350D
Original Publication Date: 1989-Sep-01
Included in the Prior Art Database: 2005-Jan-28
Document File: 1 page(s) / 11K

Publishing Venue

IBM

Related People

Hardell, WR: AUTHOR [+2]

Abstract

Disclosed is a means for an early address decode with only a partial address. This method is effective when an address must be sent across a bus in two or more parts and the address could be for one of several devices.

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Early Address Decode on a Partial Address

Disclosed is a means for an early address decode with only a partial address. This method is effective when an address must be sent across a bus in two or more parts and the address could be for one of several devices.

The early decode is made possible by sending the part of the address that specifies the device first. The device may be pre-selected based on the partial address before the full address is received. For a two-cycle address this would save one cycle.

For example, an address consists of a Segment Register (SR) and an Effective Address (EA) which are each one word wide. The address bus is one word wide. Therefore, it will require two cycles to send the address across the bus (one cycle for the SR and one cycle for the EA). If the device specific code is in the SR, then arbitration for the device can start when the SR is received. By sending the SR first, arbitration can start before the full address is received and one cycle is saved.

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