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Article ID: 317272 - Last Review: October 27, 2006 - Revision: 1.2

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This article was previously published under Q317272


When you resume your computer that has two IDE drives connected to one cable from Standby, your computer may stop responding (hang).


This problem occurs because the IDE disk driver does not check the busy bit in the drive status before it resets the drive. This is a problem with computers that are using S3 sleep for Standby. These computers stop power to the drive instead of issuing a sleep command to the drive in the same way that the S2 standby process does. This behavior causes the drives to be reset before the drive negotiation is completed when the drives restart.

The specifications for ATAPI drives require checking the busy bit before the drive is reset. The specifications also state that the drives will ignore resets until the drives are synchronized and until they are ready to operate after negotiation. As of July 2002, some drives do not do this. This behavior can cause computers with two drives to start with both drives programmed to be master on the same cable. When this behavior occurs, your computer may stop responding (hang).


To resolve this problem, obtain the latest service pack for Windows XP. For additional information, click the following article number to view the article in the Microsoft Knowledge Base:
322389  ( ) How to Obtain the Latest Windows XP Service Pack
Microsoft provides an Atapi.sys driver that waits for the drives to finish negotiation before the reset command is sent. This wait is controlled by the following DWORD registry key entry:
The default behavior of this fix is for Atapi.sys not to wait before the reset command is issued. This behavior occurs because the hotfix is in place but the registry key does not exist or the value of the registry key is set to 0.

If you experience the symptoms that are described in this article, you must create the registry key and set the value to 1. When you do so, Atapi.sys waits before sending the reset commands to the drive and prevents the computer from becoming unresponsive.

The English version of this fix should have the following file attributes or later:
   Date         Time   Version      Size    File name
   08-16-2002  10:31am 5.1.2600.55 87,168   Atapi.sys


Microsoft has confirmed that this is a problem in the Microsoft products that are listed at the beginning of this article. This problem was first corrected in Windows XP Service Pack 1. This hotfix is included with SP1. When this hotfix is installed by SP1, the default behavior remains unchanged and Atapi.sys sends the reset command. If your computer exhibits these symptoms after you apply SP1, you must create the registry key mentioned in the "Resolution" section of this article and set the value to 1 to turn on the delay.


This issue is mainly hardware related and also exists in Windows 2000. For additional information about your computer not responding when you resume from S3 state in Windows 2000, click the article number below to view the article in the Microsoft Knowledge Base:
323153  ( ) Computer May Hang During Resume from S3 Standby with Two IDE Drives

  • Microsoft Windows XP Home Edition
  • Microsoft Windows XP Professional
kbhotfixserver kbqfe kbbug kbenv kbfix kboswin2000fix kbwinxpsp1fix KB317272
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