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aristarchus [soylentnews.org] writes:

More details on Perseverance, at Gizmodo [gizmodo.com].

As we watched NASA put a rover on Mars last month, it definitely seemed like the agency had to be using some sort of high-tech processor in its machine. Surely the rover is built on something much more powerful than the components in devices us civilians use, right? But while NASA is technically using a specialized processor to power the Perseverance rover, it’s not far removed from the world of consumer electronics—about 23 years ago.

NewScientist reports that the Perseverance rover is powered by a PowerPC 750 processor, which was used in Apple’s original 1998 iMac G3—you remember, the iconic, colorful, see-through desktop. If the PowerPC name sounds familiar, it’s probably because those are the RISC CPUs Apple used in its computers before switching to Intel. (Although now the company is back on the RISC train with its homegrown M1 processor.)

The PowerPC 750 was a single-core, 233MHz processor, and compared to the multi-core, 5.0GHz-plus frequencies modern consumer chips can achieve, 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 is making an educated guess on what instructions the CPU is going to process as a way to improve efficiency. The more information that’s processed, the better the chip gets at predicting what it needs to do next.

However, there’s a major difference between the iMac’s CPU and the one inside the Perseverance rover. BAE Systems manufactures the radiation-hardened version of the PowerPC 750, dubbed RAD750, which can withstand 200,000 to 1,000,000 Rads and temperatures between −55 and 125 degrees Celsius (-67 and 257 degrees Fahrenheit). Mars doesn’t have the same type of atmosphere as Earth, which protects us from the the sun’s rays, so one flash of sunlight and it’s all over for the Mars rover before its adventure can begin. Each one costs more than $200,000, so some extra protection is necessary.

So, not off the shelf, exactly. One Million Rads? Nothing like a CPU that survives, even if you do not.

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