| United States Patent | 6,260,134 |
| Zuraski, Jr. , et al. | July 10, 2001 |
Fixed shift amount variable
length instruction stream pre-decoding for start byte
determination based on prefix indicating length vector presuming
potential start byte
Abstract
A predecode unit is configured to predecode a fixed number of instruction bytes of variable length instructions per clock cycle. The predecode unit outputs predecode bits which identify the start byte of an instruction. An instruction alignment unit uses the start bits to dispatch the instructions to a plurality of decode units that form fixed issue positions. In one embodiment, the predecode unit identifies a plurality of length vectors. Each length vector is associated with one of the instruction bytes predecoded in a clock cycle and identifies the length of an instruction if an instruction starts at the instruction byte corresponding to the length vector. A tree circuit determines in which instruction bytes instructions start.
| Inventors: | Zuraski, Jr.; Gerald D. (Austin, TX); Ahmed; Syed F. (Austin, TX); Miller; Paul K. (McKinney, TX) |
| Assignee: | Advanced Micro Devices, Inc. (Sunnyvale, CA) |
| Appl. No.: | 184750 |
| Filed: | November 2, 1998 |
| Current U.S. Class: | 712/210; 712/204; 712/213 |
| Intern'l Class: | G06F 009/38 |
| Field of Search: | 712/204,210,213 |
References Cited [Referenced By]
U.S. Patent Documents
| 5586277 | Dec., 1996 | Brown et al. | 712/210. |
| 5619666 | Apr., 1997 | Coon et al. | 712/208. |
| 5758116 | May., 1998 | Lee et al. | 712/210. |
| 5809272 | Sep., 1998 | Thusoo et al. | 712/210. |
| 5809273 | Sep., 1998 | Favor et al. | 712/210. |
| 5819059 | Oct., 1998 | Tran | 712/213. |
| 5822558 | Oct., 1998 | Tran | 712/213. |
| 5845099 | Dec., 1998 | Krishnamurthy et al. | 712/204. |
| 5941980 | Aug., 1999 | Shang et al. | 712/204. |
| 5948096 | Apr., 1999 | Ginosar et al. | 712/210. |
| Foreign Patent Documents | |||
| 0 417 013 | Mar., 1991 | EP. | |
Primary Examiner: Kim; Kenneth S.
Attorney, Agent or Firm: Conley, Rose & Tayon, PC,
Christen; Dan R.
Last Updated : Sun Mar 9 23:16:03 EST 2008
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