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Earlier I inserted a SATA drive into a simple one drive backplane I have. After a "detect hardware changes" the drive appeared, and worked correctly. Later, I removed it.

Since that time, my primary SATA drive, a Western Digital Caviar Black 640GB, which was never disconnected, is extremely slow, on the order of 4.0MB/second maximum transfer rate.

The first thing I considered is that the drive might be failing, but it passes the DataLifeguard Quick Test and Windows chkdsk. While this cannot rule out a hardware problem, it indicates against it.

Can my insertion and removal of another SATA drive have reset the connection into some very slow compatibility mode? How do I fix it? If that is not the problem, what else could cause this?

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up vote 3 down vote accepted

Sure enough, the controller channel had fallen back to PIO from Ultra DMA 5.

The solution was:

  1. Find the sub-key for the controller channel within:

    HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Class\{4D36E96A-E325-11CE-BFC1-08002BE10318}
    
  2. Delete MasterIdDataChecksum and SlaveIdDataChecksum

  3. Reboot

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+1 For the smart explanation and for sharing the solution! –  Alain Pannetier Jun 4 '11 at 8:33
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