What does a CacheCARD do?
The cachecard caches the tivo database so that it doesn't need to access the hard drive.
The video functions are real time - they must complete by a deadline otherwise the video stream will fail. A hard drive can do this job but it is working all the time - seeking back and forth between reading and writing different video streams.
The problem is when you use the user-interface it has to access the database which is also on disk. Simple operations may still require 100,000 database reads and these operations get lower priority than the video streams.
The cachecard is a true cache - just like a cache in a cpu.
The TiVo *thinks* it is accessing the hard drive to read the database, but if it is in the cache then the cache will respond with the same data but do so instantly rather than having to wait for a chance to access the hard drive, wait for the drive to seek, and wait for the data.
The end result is that user-interface operations run several times faster, improving the whole user-interface.
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