(12) United States Patent ao) Patent No.: us 6,631,440 B2
Jenne et al. (45) Date of Patent: Oct. 7,2003
(54) METHOD AND APPARATUS FOR
SCHEDULING MEMORY CALIBRATIONS
BASED ON TRANSACTIONS
(75) Inventors: John E. Jenne, Houston, TX (US);
Sompong P. Olarig, Cypress, TX (US)
(73) Assignee: Hewlett-Packard Development Company, Houston, TX (US)
( * ) Notice: Subject to any disclaimer, the term ol this patent is extended or adjusted under 35 U.S.C. 154(b) by 178 days.
(21) Appl. No.: 09/726,739
(22) Filed: Nov. 30, 2000
(65) Prior Publication Data
US 2002/0065981 Al May 30, 2002
(51) Int. CI.7 G06F 13/00
(52) U.S. C I 711/105
(58) Field of Search 711/105; 710/112
(56) References Cited
U.S. PATENT DOCUMENTS
6,182,177 Bl * 1/2001 Harriman 710/112
6,304,932 Bl * 10/2001 Ziegler et al 710/112
6,321,233 Bl * 11/2001 Larson 707/201
DirectRambusTMRIMMTMModule Specification Version 1.0, Rambus Inc., SL-0006-100 (32 p.), 2000.
Rambus®RIMMTMModule (with 1281144Mb RDRAMs), Preliminary Information, Document DL0084 Version 1.1 (12 p.).
Direct RDRAMTM256/288-Mbit (512Kxl6/18x32s), Preliminary Information Document, DL0060, Version 1.01 (69 p.).
* cited by examiner
Primary Examiner—David L. Robertson (57) ABSTRACT
A computer system includes a memory controller that controls and formats transactions with a high speed memory. The memory controller includes a read queue, a write queue, and various other queues in which memory transactions may be stored pending execution. The memory controller periodically executes calibration cycles, such as temperature calibration cycles to the memory to reduce memory errors. The temperature calibration cycles may include an idle state during which no read transactions can be executed. The memory controller includes arbitration logic that reduces latency by issuing read transaction first. Once reads have been issued, the arbitration logic executes any pending temperature cycles. During the idle period of the calibration cycle, the arbitration logic schedules write transactions, and transactions to memory from other queues and devices, including precharge transactions, row activate transactions, refresh cycles, and other calibration cycles.
15 Claims, 11 Drawing Sheets