06275885 is referenced by 43 patents and cites 5 patents.

A computer is provided having a bus interface unit coupled between a CPU bus, a peripheral bus (i.e., PCI bus and/or graphics bus), and a memory bus. The bus interface unit includes controllers linked to the respective buses, and a plurality of queues placed within address and data paths between the various controllers. The peripheral bus controller can decode a write cycle to memory, and the processor controller can thereafter request and be granted ownership of the CPU local bus. The address of the write cycle can then be snooped to determine if valid data exists within the CPU cache storage locations. If so, a writeback operation can occur. Ownership of the CPU bus is maintained by the bus interface unit during the snooping operation, as well as during writeback and the request of the memory bus by the peripheral-derived write cycle. It is not until ownership of the memory bus is granted by the memory arbiter that mastership is terminated by the bus interface unit. Accordingly, the bus interface unit keeps CPU-derived cycles off the CPU bus to ensure memory arbiter grants ownership to a write cycle from the peripheral bus. In this fashion, data from the peripheral bus can be stored in system memory before accessing that data by a CPU read cycle. The number of snoop cycles which the bus interface unit can initiate is determined by configuration registers programmed during power on, reset or boot up of computer.

Title
System and method for maintaining ownership of a processor bus while sending a programmed number of snoop cycles to the processor cache
Application Number
9/164191
Publication Number
6275885 (B1)
Application Date
September 30, 1998
Publication Date
August 14, 2001
Inventor
Robert A Lester
Houston
TX, US
John E Larson
Plano
TX, US
Michael J Collins
Tomball
TX, US
Kenneth T Chin
Cypress
TX, US
Agent
Conley Rose & Tayon P C
US
Agent
Kevin L Daffer
US
Assignee
Compaq Computer
TX, US
IPC
G06F 13/00
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