> > do I really need to update my current CHD files ?
> I don't know why anyone would update all their samples or CHD files for a "u"
> version. From my understanding, "u" releases are like development snapshots between
> major releases. It's entirely possible that this new 7-zip and FLAC stuff may change
> before MAME 0.146 is released.
This is, of course, a very good point. There is no harm in using v4 at all. v5 CHD's share the same SHA1 hashes as v5, just use alternate compression (which is selectable by user). Just know, once you convert, those CHD's cannot be used on anything earlier that 0.145u1 and it is not a trivial effort to convert it back to v4. I'm avoiding it (for those compatibility reasons) because I need to be able to test older version for bug testing. Others may not care, but know what you are getting into. There is no RUSH unless a version change becomes mandatory, which this is not.