Am I right in thinking that a hard drive that is faulty when connected to the M/B (IDE) - it won't sustain DMA mode, keeps going back to PIO (I spent weeks troubleshooting this - the drive is faulty in the end) would work fine if used as an external drive via a USB 2.0 cable? Or would the DMA fault somehow affect its performance even as an external drive?
You should diagnose why it wants to run in PIO. There's a reason for that, and if the drive was faulty it wouldnt work properly with PIO also.
Windows switches to PIO pretty agressively; if a bad SATA cable or EMI causes bitflips, the checksum errors start to skyroof. Windows will quickly stop using DMA, and use PIO as 'fallback emergency solution'.
So PIO is not really the problem, it's probably a sign of a deeper problem. Did you test:
- SMART error log (please post it here if possible, using HDTune)
- surface media scan (not chkdsk - a SURFACE scan)
- replace SATA cable - try other SATA port also
- monitor SATA power cable voltages directly using voltmeter
Hi. I did all that (apart from measure voltage with a voltmeter) in my extensive troubleshooting (thread was on this forum a few months back). Conclusion was that the drive was faulty: I got a refund in the end (awful supplier, had to go through Amazon's legal service) but they never asked for the drive back, so I am left with it. It's not a SATA drive by the way, but (P)ATA.
I am not interested in getting it to work as an internal drive any more - just thought I could use it as extra external storage one day, but maybe there is a deeper problem that would affect that, as you say.
If you put it into an external case, you'll avoid the PIO problem. But if there truly is a problem with the drive which prevents it from reliably transferrring data in DMA mode, you risk data corruption if the external case chipset isn't smart enough to deal with it intelligently. And USB 2.0 can be a lot slower than a modern drive is capable of.