And they are then no longer so smooth running and cool as the 5400 series from Seagate. Currently in my copy was a ST9500424AS Seagate, so a 7200 drive with 16MB cache installed. This has very high vibrations and can be heard in contrast to 5400! Under load it increases in the external housing loosely to well over 45 degrees. Since the disk logs as Seagate USB device, you can query the actually built plate only with SMART monitoring tools, such as HDsentinel, via the USB port, and since then came the nasty surprise with the 7200 revolutions.
From the 4th digit of the serial number can be both variants distinguish from the outside in my experience: 5400, 8MB cache, quiet + cool, is installed ST9500325AS: SN # 2GH5xxxx 7200, 16MB cache, loud and very hot, is installed ST9500424AS: SN # 2GHWxxxx
