Don’t be too dazzled. I’ve spent years in that business (couple of years ago, “I” had nearly 160 of those Top 500 on the list). There’s one hell of a lot of gamesmanship by vendors, and Linpack tests are not the best way to determine a computer’s true capabilities.
Let's not forget the acronym "MIPS" when used to test performance... "Meaningless Indicator of Performance" (as opposed to "Millions of Instructions Per Second.)
Mark