A few days ago, NASA sent a rover to Mars to conduct research. You would expect the agency to use some kind of high- end processor for this rover. Indeed, NASA is technically using a specialized processor to power the Perseverance rover, but it’s not that far removed from consumer electronics, especially compared to the ones that were available about 23 years ago. NewScientist magazine reports that NASA’s Perseverance rover is powered by a PowerPC 750 processor , which was used in ’s original iMac G3 back Apple in 1998.
The name PowerPC may sound familiar, probably because they are the RISC CPUs that Apple used in its computers before switching to Intel.
The PowerPC 750 was a single-core, 233MHz processor, and compared to modern multi-core chips with 5.0GHz-plus frequencies, 233MHz is incredibly slow. But the 750 was the first to incorporate “dynamic branch prediction,” which is still used in modern processors today. Basically, the CPU architecture makes a educated guess about which instructions the CPU will process in order to improve efficiency. The more information it processes, the easier it is for the chip to predict what to do next.
However, NASA couldn't just rely on that iMac processor. There's a significant difference between the iMac's CPU and the CPU in the Perseverance rover. BAE Systems makes a radiation-hardened version of the PowerPC 750, called the RAD750, that can withstand 200,000 to 1,000,000 Rads and temperatures between −55 and 125 degrees Celsius. Mars doesn't have the same type of atmosphere as Earth, which protects us from the sun's rays. So the processor has to have specific specifications to withstand the harsh conditions and allow NASA's Perseverance rover to do its job. Each one costs over $200,000, so extra protection.
But why would NASA want to use a processor from the 1990s? As experts say, the choice is not about cost. It's just that these want them to do researchersbecause they're reliable. NASA's Orion spacecraft, for example, also used the same RAD750 processor.
“Compared to the Intel Core i5 in your laptop, it’s a lot slower… probably not faster than your smartphone,” NASA’s Matt Lemke said in 2014.“But we’re not so much about speed as we are durability and reliability. I need to be sure that it’s going to always work.”
From that perspective, it makes sense for NASA to go with older technology. The agency has spent $2.7 billion on the Mars mission, so it needs to rely on technology that is reliable enough to withstand the rigors of time and extreme conditions. Currently, the RAD750 processor powers about 100 satellites in Earth orbit, as well as several military satellites , and there has never been a problem.
Source: Gizmodo
