Right it does hold what you are not watching in the cache
I think you are understanding it...
There is a cache (temporary holding spot on the HD) and then there is a permanent area on the hard drive for what you set it to record.
The cache gets wiped out if you change the channel or tuen it off and the cache normally only holds about 1 1/2 hours back if you leave it on the same channel.
Right it does NOT hold what you are not watching in the cache
I think you are understanding it...