Hewlett-Packard Company

Hewlett-Packard Development Company, L.p.

R Alexis Takasugi

Mark J Simms

Charles D Smith

Stewart R Wyatt

Julie Catherine Hogan

Mark John Simms

Fintan Buckley

Kimberly K Kroll

Thomas Carter

Paula D Repman

Byte-swapping in a buffer memory system utilizes a byte-swapping register to avoid wasteful unused buffer memory spaces that may result from a data transfer of partial word data, i.e., bytes of data less than the number of bytes in a word, to the buffer memory. When a data transfer request, e.g., a write request, requires a transfer of a partial word, the partial request is written to a word in the buffer memory, and is also stored in the byte-swapping register. In a subsequent data transfer request, the partial word stored in the byte-swapping register is combined and concatenated with sufficient bytes of data of the subsequent data transfer request to produce a complete word. The complete word is written in the word in the buffer memory, replacing the previously stored partial word, and thus fills the previously unused buffer memory space.

Byte-swapping for efficient use of memory

Apparatus and method for storing retrievable boundary information into a buffer memory of a receiving device. In one arrangement, the boundary information is used to indicate where a block of data ends in the buffer memory. In another arrangement, the boundary information is used to indicate where a burst begins and ends in the buffer memory. This is accomplished by the use of boundary indicators and following a set of organization rules as data and boundary indicators are written into the buffer memory. As a result, during a later buffer read operation the data and the boundary information can be retrieved and identified.

Apparatus and method for storing retrievable boundary information into a

A system for managing burst data transfers from a sending device to the buffer memory of a receiving device and for managing read operations upon the buffer memory after receiving data. In one arrangement, the system includes data management apparatus that is used in a tape storage device. The data management apparatus uses a Start of Burst pointer, a Current Position pointer and a Tape Mechanism pointer to simplify several functions. These functions include the determination of whether to enable a burst from a sending device and the determination of whether to perform a series of read operations upon the buffer memory. In addition, the Start of Burst pointer and the Current Position pointer are used to re-write a burst into the buffer memory if a previously received burst is determined to be invalid.

Burst transfer management system utilizing pointers to ensure that there

Data transfer methods and systems are described. The methods and systems permit the transferring of data which is organized into a plurality of records from a readable data storage medium to a host system with reductions in overhead and processing complexity. In a preferred embodiment, the readable data storage medium comprises a tape drive and the records have variable lengths. A data transfer processor is provided and is operably configured for coupling between the host system and the tape drive. A first record length parameter value is defined and describes a length of at least one record which is to be transferred from the tape drive to the host system. A first record having a length corresponding to the first record length parameter value is read from the tape drive and into a temporary record-holding location. Reading of additional records from the tape drive continues until a record is read having a length which is different from the length of the first-defined record length parameter value. In one aspect, the reading of the records is discontinued and records stored in the temporary record-holding location having lengths corresponding to the record length parameter value are transferred to the host system. Reading of additional records from the tape drive can continue. In a preferred embodiment, the length of the first record which is read into the record-holding location is used to define the record length parameter value; and, after the transfer of all of such records, the record length parameter value can be redefined to comprise the length of the record having the different length. Reading can then continue of additional records having lengths corresponding to such redefined record length parameter value until a different length record is encountered. Processing can continue as described until a desired number of records are transferred to the host system.

Data transferring system reading and temporarily storing a record until

Burst-mode data transfers between a SCSI host bus adapter and at least one SCSI bus device interface adapter are implemented by hardware. For a first embodiment of the invention, the device interface adapter is equipped with a first, second and third data registers, a comparator, a subtractor, and control logic in the form of an application specific integrated circuit. When a burst-mode transfer is requested, the first register is programmed with a value corresponding to the length of the transfer in bytes, and the second register is programmed with the maximum possible number of bytes in a burst. The comparator then compares the value in stored in the first register with the value stored in the second register and determines which is the smaller. The smaller of the two values is written to the third register. The subtractor then subtracts said third value from said first value to obtain a remainder value. The first value is then replaced with a new first value equal to said remainder value. The control logic orchestrates the steps of comparing said first and second values, storing the smaller of said first and second values in said third register, subtracting said third value from said first value to give a remainder value, replacing said first value with a new first value equal to said remainder value, and causing the steps of comparing, storing, subtracting and replacing to be repeated until said third value is equal to zero. Initial loading of the first and second registers is performed by either the control logic or by a microprocessor. For an alternate embodiment of the invention, the control logic, the comparator and the subtractor are replaced by a microprocessor.

System for implementing hardware automated control of burst mode data

A tape storage device is used in conjunction with a host computer to archive data. The storage device has interface logic that buffers blocks of data from the host computer in a memory buffer. The interface logic processes data as the data is received to create a processed data block that is smaller in size than the original, unprocessed data block. While receiving elements of the data block, the interface logic repeatedly determines the amount of free memory in the memory buffer, and temporarily suspends the block transfer whenever the amount of free memory falls below a predetermined threshold. The block transfer is resumed when the amount of free memory becomes equal to or greater than the threshold. This utilizes nearly all available memory, while preventing buffer overflow, without any need to perform complex calculations to predict the size of the data block after processing.

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Eagle, ID, United States of America

R Alexis Takasugi