Electrical computers and digital data processing systems: input/ – Input/output data processing – Input/output access regulation
Reexamination Certificate
1998-12-18
2001-10-09
Lee, Thomas (Department: 2182)
Electrical computers and digital data processing systems: input/
Input/output data processing
Input/output access regulation
C710S029000, C710S036000, C710S039000, C710S052000, C710S244000, C709S241000, C709S232000, C711S145000, C711S151000, C711S158000
Reexamination Certificate
active
06301627
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates generally to information processing systems and more particularly to an improved information transfer methodology in a computer related environment.
BACKGROUND OF THE INVENTION
As the sheer number of computer systems and computer system applications continues to increase, there is also an increasing need for improved and more efficient data management and data processing techniques. Increased processing speeds and bandwidth capabilities within computer systems require enhanced control techniques in order to minimize traffic congestion and optimize data flow efficiency.
Generally, elements in the path of data flow from an I/O (input/output) system to system memory can neither re-order write operations nor re-order read operations with respect to write operations. When data is sent or transferred from one device to another in a computer system, the data packages are sequenced in the order sent. This ordering process, which is enforced and required for example, by system bus architectures, (such as the PCI Local Bus Specification, Rev. 2.1, Jun. 1, 1995, which is included herein by reference), may cause performance limitations in the system.
In the past, architectures have not made it possible for I/O devices to inform the system which operations need to be ordered and which ones do not. So, for example, operations, where programs are being paged out from system memory to a DASD (direct access storage device), frequently at multiple pages at a time, do not need to have each data block that is read from system memory to be ordered with respect to write operations to system memory. The operations are independent due to the fact that the page is not being modified at the same time it is being paged out. In general, data being read by an I/O device will not be changing. One place where this might not be true is in read operations with I/O control block areas where there is the likelihood that read operations may need to be kept in order with write operations to that same area, otherwise improper operations may result. Further, where programs are being brought into system memory from a DASD, each separate data block write operation from the DASD does not need to be ordered with respect to one another so long as all of the transfers complete before the I/O operation is complete. On the other hand, write operations with I/O control block areas will most likely need to be kept in order with one another in order to avoid any improper operations which might result.
Thus, there is a need for an improved information processing methodology and system in which information is more efficiently transferred between system devices during information processing transactions.
SUMMARY OF THE INVENTION
A method and apparatus is provided in which I/O data is tagged to identify an ordering of data transfer requests relative to other data transfer requests. Write and Read transaction requests are tagged for ordering relative to previous write requests. Current read and write transaction requests are selectively allowed to bypass earlier write transaction requests which have been temporarily delayed in transfer. In one embodiment, the bypass occurs in a bridge buffer positioned between I/O devices and a system memory. In another embodiment, the methodology is applied where a split read or write transaction includes reserved bits in the attribute fields which are utilized to indicate if the transaction is allowed to bypass previous write transactions.
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Neal Danny Marvin
Thurber Steven Mark
International Business Machines - Corporation
Lee Thomas
Leeuwen Leslie A. Van
Nguyen Tanh
Wilder Robert V.
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