Those of you at work today on cutting-edge systems understand that the name of the game in the high-performance business is to provide as much performance as possible, at a reasonable cost, and subject to the ironclad rule that the system must be reliable.

As you increase performance (for example: turn up the clock) every system inevitably plummets off the edge of a "reliability cliff".

It is your responsibility as a designer to make your system run as close as possible to this cliff without ever actually falling off.

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http://www.pisaonline.it/pisa/town/pagine/torre2.htm [excerpts]
Construction begun in 1173 and it must have been suspended at the completion of the third ring, around ten years later, since a subsidence of the soil of between 30 and 40 cm. had thrown the tower out of the perpendicular, causing an initial overhang of circa 5 cm.
[Construction] was once again begun in 1275 by Giovanni di Simone, who added three more levels, correcting the axis of the Campanile.
In 1284 the six stories of loggias were to all effects finished, bringing the height of the building to 48 m.
[Today the tower] rises... ...56 m over the level of the countryside... ...the progression of the overhang, despite all attempts so far made to bring it to a halt, is about 1.2 mm per year.