Compaq Computer Corporation, Inc.

Hewlett-packard Development Company, L.p.

Usha Rajagopalan

Sompong Paul Olarig

Ronald Timothy Horan

Morrel O Jones, Iii

A computer system having at least one central processing unit, system memory, and a core logic capable of accepting an AGP bus is provided with an AGP to AGP bridge connected to the standard AGP bus. The AGP to AGP bridge can accommodate two or more AGP-compatible devices that can be accessed through the standard AGP bus via the AGP to AGP bridge. A PCI to memory bridge is also provided within the AGP to AGP bridge so that PCI devices may be connected to the AGP to AGP bridge. The AGP to AGP bridge is fitted with an overall flow control logic that controls the transfer of data to or from the various AGP devices and the standard AGP bus that is connected to the core logic of the computer system. The AGP to AGP Bridge can utilize a standard 32-bit AGP bus as well as (two) dual 32-bit buses to enhance bandwidth. In an alternate embodiment of the invention, the dual 32-bit buses can be combined to form a single 64-bit bus to increase the available bandwidth. Alternate embodiments of the AGP to AGP Bridge can accommodate the single 64-bit AGP bus for increased performance. Another alternate embodiment can accommodate peer-to-peer transfer of data between AGP busses on the bridge.

Apparatus, method and system for accelerated graphics port bus bridges

The present invention makes it possible to safely hot plug a PCI expansion slot connected to a 64 bit, 66 Megahertz PCI bus. The PCI bus comprises a plurality of signal lines connecting a PCI Controller to the expansion slot. On each signal line there is a quick switch disposed thereon to detach the signal line from the expansion slot. A bus_enable signal activates the quick switches and a Req_64 mode line to detach or attach the PCI bus from the expansion slot. The Req_64 mode line bypasses the quick switches and goes through a crossbar switch. The crossbar switch has its open state set to an active low wherein the 64 bus mode is thereby communicated to the card as an active low even when the other signal lines of the bus are in a high disconnected state.

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Houston, TX, United States of America

Usha Rajagopalan