You can look at the DVR Diagnostics. And page down in the cable card menu to see how many seconds it has been since a restart.
BOLT(4TB)x2/Roamio Pro (5TB Red)
TiVo Mini x4
Roamio Basic(1TB Red)/Roamio Basic refurb(3TB green)
53TB unRAID2--41TB unRAID3--35TB unRAID1a