Seagate ST3400620A Serial ATA Native Command Queuing (670K, PDF)
Seagate ST3400620A - Barracuda 7200.10 - Hard Drive Manual
UPC - 000068213367
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- Seagate ST3400620A | Serial ATA Native Command Queuing (670K, PDF) - Page 1
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 - Seagate ST3400620A | Serial ATA Native Command Queuing (670K, PDF) - Page 2
most anticipated features introduced in the Serial ATA II: Extensions to Serial ATA 1.0 Specification, download available at www.serialata.org. NCQ command protocol in Serial ATA that allows multiple commands to be outstanding within a drive at the same time. Drives that support NCQ have an internal - Seagate ST3400620A | Serial ATA Native Command Queuing (670K, PDF) - Page 3
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 algorithm. The best known algorithm may sound, most of today's hard drives in the desktop environment still - Seagate ST3400620A | Serial ATA Native Command Queuing (670K, PDF) - Page 4
but instead takes into account the rotational position of the drive head in determining the best command to service next. A second-order optimization is to use a providing the additional benefit of improved endurance. Serial ATA II provides an efficient protocol implementation of tagged command queuing called - Seagate ST3400620A | Serial ATA Native Command Queuing (670K, PDF) - Page 5
proceed without any software intervention. This is the means by which the drive can effectively re-order commands since it can select the buffer to two NCQ commands that were added as part of the NCQ definition in Serial ATA II, Read FPDMA Queued and Write FPDMA Queued. The Read FPDMA Queued - Seagate ST3400620A | Serial ATA Native Command Queuing (670K, PDF) - Page 6
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 be between 0 and 31, although the drive can report support for a queue depth less than 32. In this case, - Seagate ST3400620A | Serial ATA Native Command Queuing (670K, PDF) - 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 field is used to support out-of-order data delivery, also referred to as nonzero buffer offset within the specification. Non-zero buffer offset allows the drive to transfer data - Seagate ST3400620A | Serial ATA Native Command Queuing (670K, PDF) - Page 8
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 that the host effectively only services one interrupt rather than two the same time. However, the best performance improvement can only be achieved - Seagate ST3400620A | Serial ATA Native Command Queuing (670K, PDF) - 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, - Seagate ST3400620A | Serial ATA Native Command Queuing (670K, PDF) - Page 10
Serial ATA Native Command Queuing &overlap); // Contains event and offset for asynchronous // operation // // Make sure there was NCQ are realized when a queue of commands is built up in the drive such that the drive can optimally re-order the commands to reduce both seek and rotational latency. - Seagate ST3400620A | Serial ATA Native Command Queuing (670K, PDF) - Page 11
has been with Intel for 6 years. Joni Clark, Product Marketing Manager, Seagate Technology Joni Clark is a product marketing manager for desktop interfaces at Seagate Technology, focusing on promoting Serial ATA technology to customers from system builders to end users. Her current responsibilities - Seagate ST3400620A | Serial ATA Native Command Queuing (670K, PDF) - Page 12
Serial ATA Native Command Queuing 12
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