Electrical computers and digital data processing systems: input/ – Intrasystem connection – Bus access regulation
Reexamination Certificate
1998-06-08
2001-02-06
Beausoliel, Jr., Robert W. (Department: 2781)
Electrical computers and digital data processing systems: input/
Intrasystem connection
Bus access regulation
C710S108000, C710S108000
Reexamination Certificate
active
06185645
ABSTRACT:
BACKGROUND
1. Field of the Invention
The present invention relates to fault tolerance in computer systems, and more particularly to a method for removing power and signals from a bus card that is inadvertently removed from a computer system during a “hot swap” operation while the computer system is running.
2. Related Art
The demand for reliability in computer systems has led to the development of computer systems that support “hot swapping” of bus cards. This allows a computer system to continue operating while a bus card is removed from the computer system, and while a new bus card is inserted into the computer system. In this way, failed system components located on bus cards can be replaced without shutting down the computer system. The other bus cards in the computer system can continue to function while the defective bus card is being replaced.
Existing hot swapping systems typically use software routines to remove power from a bus slot before a bus card is removed from the bus slot. A similar software routine is used to “power up” a new bus card after the new bus card is inserted into the bus slot. These power removal and power up functions prevent the bus card and the computer system from being damaged when the bus card is removed and/or replaced.
However, hot swapping can lead to other problems. If a computer system operator is not careful during the hot swapping process, the computer system operator may inadvertently remove the wrong bus card. This is an easy mistake to make because bus cards are typically packed close together and are often similar or identical in appearance. In order to guard against inadvertent removal, the computer system operator must take special care to power down the proper bus card, and to properly identify the powered down bus card for removal.
Some existing systems provide light emitting diodes (LEDs) near each bus card to indicate whether or not the bus card is receiving power. By examining these diodes, the computer system operator can locate the proper card to remove. However, these LEDs are often a number of inches from their corresponding bus card connectors, and the bus cards are often packed very closely together. Consequently, an operator can still easily remove the wrong bus card during the hot swapping process, in spite of the presence of the LEDs.
Removal of the bus card while the computer system is operating can have serious consequences. At a minimum, the system is likely to “hang” while waiting on an uncompleted bus transaction involving the removed bus card. At worst, removal of the bus card from an operating computer system can cause damage to the computer system and/or the bus card.
What is needed is a mechanism that removes power and signals from a bus card before the bus card can be inadvertently removed from a computer system.
SUMMARY
One embodiment of the present invention provides a method for removing power and signals from a bus card in a computer system when the bus card is inadvertently removed from the computer system while the computer system is operating. The method includes sensing a movement of the bus card from a bus connector in the computer system while the computer system is operating, and in response to the movement, removing power and signals from the bus card. The present invention can thereby prevent damage or failure of the computer system when a bus card is inadvertently removed from the computer system by powering down the bus card and/or removing signals from the bus card before it is completely removed.
Another embodiment of the present invention includes sensing an insertion of the bus card into the bus connector, and in response to the insertion of the bus card, resetting the bus card. In a variation on this embodiment, resetting the bus card includes reinitializing the bus card to an initial state. In another variation, removing power from the bus card includes saving state from the bus card to the computer system, and resetting the bus card includes restoring the state to the bus card from the computer system.
In another embodiment of the present invention, removing power from the bus card includes waiting until a bus transaction involving the bus card completes before removing the power. In another embodiment, removing power from the bus card includes waiting until the computer system completes a task involving the bus card before removing power.
In another embodiment of the present invention, removing power from the bus card includes isolating the computer system from the bus card using isolation buffers interposed in signal lines coupling the bus connector to the computer system. Another embodiment of the present invention includes limiting rapid influxes of current into the bus card using an inrush limiter.
In another embodiment of the present invention, sensing the movement of the bus card includes sensing a movement of the bus card using a mechanical switch. In another embodiment, sensing the movement of the bus card includes using an optical switch. In yet another embodiment, sensing the movement of the bus card includes sensing a movement of the bus card using a switch located inside the bus connector at a furthest insertion distance of the bus card into the bus connector. In yet another embodiment, sensing the movement of the bus card includes sensing a movement of the bus card using a switch located outside of the bus connector. In another embodiment, sensing the movement of the bus card includes sensing a movement of the bus card using two switches located at opposing ends of the bus connector.
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Fleming, III Hoyt A.
Klein Dean A.
Beausoliel, Jr. Robert W.
Micron Electronics Inc.
Park & Vaughan LLP
Vo Tim
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