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A lot of USB 2.5" enclosures are bus-powered no matter if you put an HDD or an SSD in them. Only old/underpowered USB ports may have problems.

Hmm. I've been testing various new notebook drives with "late model" notebook enclosures. They all have required an AC adapter to spin up. Some tap into the FW800 port to get enough to spin up.

Which drives and USB enclosures have you experienced as bus powered on USB only?
 
Which drives and USB enclosures have you experienced as bus powered on USB only?

A couple of chinese dirt cheap aluminum 2.5" USB cases from ebay (drives: Momentus 7200.4 500gb, Momentus 5400.6 500gb, WD Scorpio Blue 640gb), an old external 160gb 2.5" i bought like 4 years ago, and as far as datasheets are concerned pretty much every modern external 2.5" from major brands (Lacie, WD, Seagate)....

On the other hand, I have an ONNTO FW800+USB 2.5" case that is powered only on FW800 and requires an AC adapter if used with USB. But this is not the most common scenario. I'd say it's the least common.
 
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