1. IDENTIFICATION OF PROPOSED PROJECT 1.1 Title AT Attachment Interface for Disk Drives 1.2 Proposer This project is proposed by X3T9.2. 1.3 Date Submitted June 22, 1990 2. JUSTIFICATION OF PROPOSED PROJECT 2.1 Needs The widespread use of desktop computers with a 16-bit memory bus has led to the adoption within industry of a disk drive which attaches via a subset of the personal computer AT bus. Because of their compatibility with existing personal computer AT hardware and software this interface quickly became a de facto industry standard. 2.2 Recommended Scope of Standard The intent of the standard is to specify a subset of the AT bus specifically developed for the direct attachment of peripherals. This standard will specify the mechanical and electrical characteristics as well as the methods by which commands are directed to peripherals, the contents of registers and the method of data transfers. 2.3 Existing Practice in Area of Proposed Standard There is no standard peripheral interface which can operate with a subset of the memory bus, and attached directly to a computer system's motherboard. There are channel interfaces which offer similar capabilities but require a translation into a protocol other than that used by the memory bus. 2.4 Expected Stability of Proposed Standard with Respect to Current and Potential Technological Advances Projections of the market growth for AT bus-based desktop computers are in the tens of millions, and embedding an AT bus subset in the drive reduces the cost of attaching peripherals. 3. DESCRIPTION OF PROPOSED PROJECT 3.1 Type of Document (Standard or Technical Report): Standard. 3.2 Definition of Concepts and Special Terms None. 3.3 Expected Relationship with Approved X3 Reference Models The AT Attachment interface is for use in closed systems. 3.4 Recommended Program of Work The following program of work is planned for the AT Attachment standard: o Solicit participation by press release and invite proposals o Investigate existing standards and standards projects to determine if they are applicable to the development effort. If appropriate, liaison will be established with other standards committees. o Establish functional requirements. o Prepare a draft standard based on proposals submitted and other information gathered during the initial investigation. o Testing of the standard will be done by individual and cooperative efforts by the participating membership. o Submit the proposed standard to X3 for approval. 3.5 Resources - Individuals and Organizations Competent in Subject Matter The current membership of X3T9.2 includes representatives from all parts of the computer industry from semiconductor chip manufacturers to large mainframe system manufacturers as well as Government agencies. Active participation and co-operation will be provided by members of X3T9.2. There are sufficient resources to complete the definition of the AT Attachment without delaying work on other standards. 3.6 Recommended X3 Development Technical Committees It is recommended that the development work be done in task group X3T9.2 which was responsible for developing the ESDI and SCSI standards. 3.7 Anticipated Frequency and Duration of Meetings Task group X3T9.2 meets formally every two months and holds informal working groups between the formal meetings. 3.8 Target Date for Submission of dpANS to X3 Submission to X3 of the dpANS is targeted for August, 1991. 3.9 Estimated Useful Life of Standard It is anticipated that this standard will have a life of over 10 years. 4. IMPLEMENTATION IMPACTS 4.1 Impact on Existing User Practices and Investments By providing an alternative to existing peripheral channel definitions the AT Attachment will provide users with a low cost means to attach magnetic peripherals within the chassis of the desktop computer. 4.2 Impact on Supplier Products and Support By providing a standard to define the AT Attachment, manufacturers will be able to reduce the variations that exist in presently implemented products. 4.3 Techniques and Costs for Compliance Verification The verification methods and costs associated therewith will be borne by individual manufacturers. 4.4 Legal Considerations A call for patents related to AT Attachment, in accordance with Milestone 7 of X3/SD-2 will be made. 5. CLOSELY RELATED STANDARDS ACTIVITY 5.1 Existing Standards X3.131 Small Computer System Interface (SCSI) 5.2 X3 Standards Development Projects Enhanced Small Computer System Interface (SCSI-2) 5.3 X3/SPARC Study Groups None. 5.4 Other Related Domestic Standards Efforts None. 5.5 ISO Standards Development Projects Projects in ISO JTC 1/SC25 WG4 will be established. 5.6 Other Related International Standards Development Projects None outside of X3T9. 5.7 Recommended for Close Liaison ISO JTC 1/SC25 WG4 5.8 Recommendations for Coordinating Liaison Continued participation in ISO JTC 1/SC25 WG4 meetings by X3T9 members appointed as U.S. delegates.