Moore's Law (the approximate doubling of computing power every two years) is pretty astonishing when you sit to consider it, even though it's considered almost normal today.
One place where it doesn't hold is in deep space missions. Once a probe has been launched, its computing hardware has to last without maintenance or upgrades for up to a decade, looking progressively archaic by comparison with current Earth technology. This is something we've also seen with cameras and other hardware - the image quality of pictures taken by deep space probes are probably already outclassed by those taken with your phone.
This article is a fascinating look at the requirements and capabilities of the New Horizons mission and the reasoning behind NASA's choice to use commercial hardware to handle its missions.
A closer look at the computer systems aboard the probe reveals many parts that would be considered archaic by today’s standards. However, it is important to remember that the New Horizons project is based on initial research work that began in the 1990s at a time when 32-bit computers clocked at a few hundred MHz were the norm. Secondly, space missions mandate radiation-hardened components that require a significantly longer time to build compared to the standard parts inside a consumer device. The radiation-hardening technique ensures systems continue to operate without fault under the harshest space conditions.