Complex sentence: The Advanced/36 bought the world of System/36 and SSP about five more years in the marketplace, but by the end of the 20th century, the marketplace for the System/36 was almost unrecognizable.
Split into simpler sentences: The Advanced/36 bought the world of System/36 and SSP about five more years in the marketplace. By the end of the 20th century, the marketplace for the System/36 was almost unrecognizable.