Seagate ST3500630A Serial ATA Native Command Queuing (670K, PDF)
Seagate ST3500630A - Barracuda 500 GB Hard Drive Manual
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- Seagate ST3500630A | 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 ST3500630A | Serial ATA Native Command Queuing (670K, PDF) - Page 2
how software developers can enhance their applications to take advantage of Serial ATA NCQ thereby creating higher performance applications. Introduction Accessing media on mass storage devices, such as hard disc drives (HDD), can have a negative impact on overall system performance. Unlike other - Seagate ST3500630A | Serial ATA Native Command Queuing (670K, PDF) - Page 3
today's hard drives in the desktop environment still operate exactly in this fashion. Elevators have evolved to understand that re-ordering the targets will result in a more economic and, by extension, faster mode of operation. With Serial ATA, not only is re-ordering from a specific starting point - Seagate ST3500630A | 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 ST3500630A | Serial ATA Native Command Queuing (670K, PDF) - Page 5
, PIO, etc. The drive determines this information by the particular command opcode that is issued. Therefore in order to take advantage of NCQ, commands that are specifically for NCQ were defined. There are two NCQ commands that were added as part of the NCQ definition in Serial ATA II, Read FPDMA - Seagate ST3500630A | Serial ATA Native Command Queuing (670K, PDF) - Page 6
a tag associated with it. The tag is a shorthand mechanism used between the host and the device to identify a particular outstanding command. Tag values can be between 0 and 31, although the drive can report support for a queue depth less than 32. In this case, tag values are limited to the maximum - Seagate ST3500630A | Serial ATA Native Command Queuing (670K, PDF) - Page 7
ATA Native Command Queuing To program the DMA engine for a data transfer, the drive support out-of-order data delivery, also referred to as nonzero buffer offset within the specification. Non-zero buffer offset allows the drive definition. Analogously, drives cannot send a Set Device Bits FIS before - Seagate ST3500630A | Serial ATA Native Command Queuing (670K, PDF) - Page 8
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. The host can set bits in the SActive register, while the device can clear bits in the SActive register. This ensures that updates to the SActive register require no - Seagate ST3500630A | Serial ATA Native Command Queuing (670K, PDF) - Page 9
ATA of the data can be cut in half. Using Asynchronous I/O in Windows* In Windows* applications, there are two main functions used for accessing files called file to start reading from overlap.offsetHigh = 0; // Upper 32-bits of offset overlap.hEvent = hEvent; // Event to trigger when complete - Seagate ST3500630A | Serial ATA Native Command Queuing (670K, PDF) - Page 10
Serial ATA Native Command Queuing &overlap); // Contains event , asynchronous I/O involves more code and can seem a bit cumbersome. However the performance potential of combining queuing with of commands is built up in the drive such that the drive can optimally re-order the commands to reduce - Seagate ST3500630A | 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 ST3500630A | Serial ATA Native Command Queuing (670K, PDF) - Page 12
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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