Frank J Tanzi

US Patent:

20050246507, Nov 3, 2005

Filed:

Apr 29, 2004

Appl. No.:

10/834637

Inventors:

Fadi Busaba - Poughkeepsie NY, US
Steven Carlough - Poughkeepsie NY, US
Mark Check - Hopewell Junction NY, US
Christopher Krygowski - Lagrangeville NY, US
John Rell - Saugerties NY, US
Frank Tanzi - Fishkill NY, US

Assignee:

International Business Machines Corporation - Armonk NY

International Classification:

G06F012/00

US Classification:

711154000

Abstract:

A method of pre-aligning data for storage during instruction execution improves performance by eliminating the cycles otherwise required for data alignment. The method can convert data between ASCII and Packed Decimal format, and between Unicode Basic Latin and Packed Decimal format. Conversion to Packed Decimal format is needed for decimal hardware in a microprocessor designed to generate decimal results. Converting from Packed Decimal to ASCII and Unicode Basic Latin is necessary to report Decimal Arithmetic results in a required format for the application program. To further improve performance, all available write ports in the fixed point unit (FXU) are utilized to reduce the number of cycles necessary to store results. To prevent data fetching of the unused destination data from slowing down instruction execution, the destination locations are tested for storage access exceptions, but the data for these operands are not actually fetched. A single read request from the FXU to the operand buffers effectively reads the entire destination address (up to 8 double-words of data) in a single cycle.