Microsoft KB Archive/323760

= Programming of Transfer Mode Speed Is Not Supported by Atapi.sys When You Hot or Warm Swap Drives =

Article ID: 323760

Article Last Modified on 5/30/2007

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APPLIES TO


 * Microsoft Windows XP Professional
 * Microsoft Windows XP Home Edition

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This article was previously published under Q323760



SUMMARY
Some Integrated Drive Electronics (IDE) drive bays are designed so that you can quickly change a physical drive with another drive either by hot-swapping the drive (while the computer is still running) or warm-swapping the drive (while the computer is in standby). These drive bays are most frequently on laptop computers, but may be on servers and workstations.

If the drive uses the Atapi.sys driver, a form of redetection occurs after you swap a drive. Windows is then notified of the change. However, Atapi.sys does not support redetecting and resetting the timing transfer modes during hot-swapping or warm-swapping. Therefore, in some cases in which the swapped drives support different transfer modes such as UMDA, DMA, or PIO, the resulting transfer mode of the final device may slow down, or may default to the lowest possible mode (PIO mode).



MORE INFORMATION
If you swap a drive and the resulting transfer mode is lower than the mode that the drive supports, the only way to force the drive to be redetected is to turn off the computer, swap the drive with another drive, and then restart the computer so that full redetection occurs. Then repeat the process of shutting down and swap to the original drive again. Then, shut down and swap to the original drive again. Turning the computer off and then back on does not resolve the issue if you do not swap the drive.

Keywords: kbenv kbprb KB323760

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