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I have a Windows XP system with 2 SATA hard drives - WD Raptor 300 & WD Caviar 500. The motherboard is P31 and I have UDMA enabled in the BIOS.

Now the Raptor works in DMA mode while the Caviar only works in PIO mode. So what are the possible reasons for that?

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1 Answer 1

up vote 2 down vote accepted

Windows defaults back to PIO mode if it encounters a succession of errors/timeouts while transferring data. The data transfer error cause can be various - faulty cables, faulty ports, interference, bad hard disk - to name a few.

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