Electrical computers and digital data processing systems: input/ – Intrasystem connection – Bus access regulation
Reexamination Certificate
1998-12-31
2001-06-05
Ray, Gopal C. (Department: 2181)
Electrical computers and digital data processing systems: input/
Intrasystem connection
Bus access regulation
C710S008000, C710S108000, C345S520000
Reexamination Certificate
active
06243782
ABSTRACT:
FIELD OF THE INVENTION
The present invention pertains to the field of computer systems. More particularly, this invention pertains to the field of installing an upgrade graphics device in the presence of a previously installed graphics device.
BACKGROUND OF THE INVENTION
High performance graphics devices are becoming increasingly important in today's computer systems. Computer system manufacturers commonly install graphics accelerators on add-in cards that plug into connectors that provide connection to a graphics bus such as an accelerated graphics port (AGP) bus. Graphics accelerators are also commonly installed by soldering the component directly onto computer system motherboards. The add-in card method provides the computer system manufacturer and the end user a means for installing a newer model graphics accelerator. One can simply remove the old add-in card and install a new one. The add-in card method has a drawback in that the add-in card method is more expensive than the solder-down method. The add-in card also uses more space than a device soldered directly onto the motherboard.
The solder-down method provides a cost savings over the add-in card method, but has the disadvantage of not providing a method for upgrading the graphics accelerator. If a computer system manufacturer wishes to change to a different graphics accelerator, the computer system manufacturer must redesign the motherboard. Further, the AGP bus is meant to be a point-to-point interconnect between a system memory controller and a single graphics device, and prior computer systems that utilize an AGP bus are not able to provide an upgrade option when a graphics device is already soldered onto the motherboard.
SUMMARY OF THE INVENTION
A method and apparatus for disabling a graphics device when an upgrade graphics device is installed is disclosed. The apparatus includes a bus interface that includes a plurality of bus signal buffers. The apparatus also includes a reset circuit and a disable input. The disable input receives a device disable signal. The bus interface unit places the bus signal buffers in a high impedance state when the device disable signal is asserted, and the reset circuit resets the apparatus following a device disable signal transition from asserted to deasserted.
Other features and advantages of the present invention will be apparent from the accompanying drawings and from the detailed description that follows below.
REFERENCES:
patent: 5280579 (1994-01-01), Nye
patent: 5515514 (1996-05-01), Dhuey et al.
patent: 5996037 (1999-11-01), Emnett
Michelsen Jeffery M.
Woolsey Clark T.
Intel Corporation
Ray Gopal C.
Wells Calvin
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