The SH7751R is a custom subtype created for IO-DATA by Hitachi, derived from the SH4-200 Series.
The SH7751R runs at 266MHz, "200MHz to 266MHz" Clock Up Version for NAS.
LANDISK/LANTANK is based on Debian/GNU Linux. Detailed information with LANDISK LANTANK is obtained as follows. http://iohack.sealandair.info/wiki/index.php?I-O%20HACK