Seagate ST3320620A - Barracuda 320 GB Hard Drive Manual
Serial ata native command queuing (670k, pdf)
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Summary of Contents for Seagate ST3320620A - Barracuda 320 GB Hard Drive
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Page 1: Serial Ata
July 2003 Serial ATA Native Command Queuing An Exciting New Performance Feature for Serial ATA A JOINT WHITEPAPER BY: Intel Corporation and Seagate Technology www.intel.com www.seagate.com... -
Page 2: Drive Basics
Serial ATA Native Command Queuing Summary Native Command Queuing (NCQ) is among the advanced and most anticipated features introduced in the Serial ATA II: Extensions to Serial ATA 1.0 Specification, download available at www.serialata.org. NCQ is a powerful interface/disc technology designed to increase performance and endurance by allowing the drive to internally optimize the execution order of workloads. - Page 3 Serial ATA Native Command Queuing sides of the discs, is collectively called a cylinder. Thus, data is laid out across the discs sequentially in cylinders starting from the outer diameter of the drive. One of the major mechanical challenges is that applications rarely request data in the order that it is written to the disc.
- Page 4 Serial ATA Native Command Queuing Keep in mind that re-ordering of pending commands based strictly on the ending location of the heads over the logical block address (LBA) of the last completed command is not the most efficient solution. Similar to an elevator that will not screech to a halt when a person pushes a button for a floor just being passed, HDDs will use complex algorithms to determine the best command to service next.
- Page 5 Serial ATA Native Command Queuing Native Command Queuing achieves high performance and efficiency through efficient command re-ordering. In addition, there are three new capabilities that are built into the Serial ATA protocol to enhance NCQ performance including race-free status return, interrupt aggregation, and First Party DMA.
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Page 6: Transferring Data
Serial ATA Native Command Queuing The commands also contain a force unit access (FUA) bit for high availability applications. When the FUA bit is set for a Write FPDMA Queued command, the drive will commit the data to media before returning success for the command. By using the FUA bit as necessary on writes, the host can manage the amount of data that has not been committed to media within the drive’s internal cache. - Page 7 Serial ATA Native Command Queuing To program the DMA engine for a data transfer, the drive issues a DMA Setup FIS to the host, shown in Figure 2. There are a few key fields in the DMA Setup FIS that are important for programming the DMA engine.
- Page 8 Serial ATA Native Command Queuing in the SActive register is cleared, it means that a command with that tag is not outstanding in the drive. The host and drive work together to make sure that the SActive register is accurate at all times.
- Page 9 Serial ATA Native Command Queuing an event to be signaled or by receiving a callback. Since the call returns immediately, the application can continue to do useful work, including issuing more read or write file functions. The preferred method for writing an application that needs to make several different file accesses is to issue all of the file accesses using non-blocking I/O calls.
- Page 10 Serial ATA Native Command Queuing &overlap); // Contains event and offset for asynchronous // operation // Make sure there was not an error. if ((ERROR_SUCCESS != bStatus) || (ERROR_IO_PENDING != bStatus)) fprintf(stderr, “ReadFile call failed.\n”); ExitProcess(); // Make more IO calls or do other useful work. // Check that the IO has been completed.
- Page 11 Group marketing team to lead the promotion of the Serial ATA interface. Disclaimer Copyright © 2003, Intel Corporation and Seagate Technology LLC. All rights reserved. The Intel logo is a trademark or registered trademark of Intel Corporation or its subsidiaries in the United States and other countries.
- Page 12 Serial ATA Native Command Queuing...