ExtremeTech describes it as an “Apple Airport Extreme… with wheels:”
At the heart of Curiosity there is, of course, a computer. In this case the Mars rover is powered by a RAD750, a single-board computer (motherboard, RAM, ROM, and CPU) produced by BAE. The RAD750 has been on the market for more than 10 years, and it’s currently one of the most popular on-board computers for spacecraft. In Curiosity’s case, the CPU is a PowerPC 750 (PowerPC G3 in Mac nomenclature) clocked at around 200MHz — which might seem slow, but it’s still hundreds of times faster than, say, the Apollo Guidance Computer used in the first Moon landings. Also on the motherboard are 256MB of DRAM, and 2GB of flash storage — which will be used to store video and scientific data before transmission to Earth.
The RAD750 can withstand temperatures of between -55 and 70C, and radiation levels up to 1000 gray. Safely ensconced within Curiosity, the temperature and radiation should remain below these levels — but for the sake of redundancy, there’s a second RAD750 that automatically takes over if the first one fails.
That’s not a bad description of what it is. Just as a comparison, the original iPhone, which came out 5 years ago was 412 MHz (although you can’t directly compare clock speeds of different chipsets). The soon-to-be-replaced iPhone 4S has two cores each clocked at 800 MHz and 512 MBs of ram. Most likely the phone in your pocket is more powerful than the computer system that powers the latest Mars rover.
So why are the tech spechs on Curiosity so modest? Because they can be.
The iPhone and your desktop computer run general purpose operating systems. General purpose operating systems have to do a lot of things and run all kinds of applications. A general purpose OS can be used for playing video games, editing movies, recording music, writing books, surfing the Internet, creating Websites and applications, drafting 3D models, conducting physics simulations, making video calls, etc. A general purpose OS can be made to do just about any computing task.
Curiosity runs an embedded operating system that does a limited numbers of functions, and the OS itself is the only application that is run. An embedded OS can’t run applications. Because of this, embedded OSes tend to be very reliable and efficient.
Your car has several computers inside it that run embedded OSes for specialized tasks. Nuclear reactors in power plants run on embedded OSes as well. You wouldn’t want Windows or OS X for these tasks, just as an embedded OS wouldn’t work for a smartphone.
Any device meant for space flight needs to worry about power consumption. Slower CPUs use less power. Even more ram takes up more power. Where every watt counts, the latest specs may not be the greatest idea.
This same logic applies to computing devices in every day life. Smartphones could have more powerful processors than the do and have more ram, but the more power a smartphone has and the more ram it has, the more battery power it needs. To be a true mobile device, a device needs to work for a substantial period of time away from an outlet or recharging source.