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Enhanced Presence Detection Scheme Disclosure Number: IPCOM000013548D
Original Publication Date: 2000-Jan-01
Included in the Prior Art Database: 2003-Jun-18

Publishing Venue



2 Disclosed is a system that uses a serial IC bus connection to detect the number and type of functions installed in a server. Use of 2 the serial IC bus eliminates the need for separate "Presence Detection" signals to be separately wired from each function to a central point. This serial bus connection and associated circuitry also ensures that the logic can detect that a function is present and not working versus a function that is not present. The next generation of servers will have the capability of logically being different from each other even though the base planar wiring is the same. A method must be devised to allow the Basic Input/Output System (BIOS) to determine which functions are currently installed in a server. This can be done by a serial link routed to all possible logical elements or by separate presence detection signals to each logical element. When using a serial link, the BIOS can address each logical element in the system and determine the type of element and if it is present. However, if this serial link fails on a logical element, BIOS has no way of determining if the logical element is present and not working, or the logical element is not present. Separate presence detection signals overcome this problem, but must be routed from different parts of the system (sometimes in a physically different place) to a central site and detected by BIOS. Whereas separate presence detection signals are more reliable, they are difficult to manage because they consume a large number of General Purpose Input/Output (GPIO) ports in any logical detection element. A combination of both methods implemented on the base planar provides the best solution for accurately detecting logical elements within a server environment. As shown in the figure below, a service processor first reads the Vital Product Data (VPD) device installed on the server planar to 2 determine the number of serial IC devices installed. Reading these serial devices ensures that BIOS can read the exact number of 2 serial IC devices that are required to be installed in the complete system. By comparing the data obtained from these serial I2C 2 devices with the VPD table BIOS can accurately determine if the actual installation of IC devices compares with the projected 2 installation of IC devices. If the actual does not match the projected, the planar card is bad and needs to be replaced. If the actual 2 matches the projected, BIOS reads each serial IC device and determines the number of logical system elements present by reading 2 the "Presence Detect" signals as inputs to the IC devices. BIOS then constructs a logic device table by mapping the data contained 2 in the VPD device and the data read from the "Presence Detect" input signals from the I C serial devices. Once this table is constructed, BIOS can then verify the proper operation of all installed logical elements by executing a diagnostic program. Devices not working can properly be identified. There is no ambiguity whether the logical element is installed and not working, or not installed as in previous methods. 1