I remain absolutely floored by just how old the CPUs are in spacecraft.

[T]he 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.

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.

It’s really amazing how much you can do on old hardware. We are really spoiled. I am constantly reminded that the computer I took to college had a clock speed of about half that of my current wristwatch. My watch.1

Of course, there’s a very good reason for using such an antique:

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).

Oh, and by the way: the RAD750 costs $200,000! Yup. Worth it for the reliability—the whole mission is running$2.7B.

Do check out the source article on NewScientist if you can (warning: paywalled).

https://gizmodo.com/a-1990s-imac-processor-powers-nasa-s-perseverance-rover-1846380844

1. I understand that’s not exactly a—how shall we say—apples-to-apples comparison. ↩︎

##### Jim Bagrow
###### Associate Professor of Mathematics & Statistics

My research interests include complex networks, computational social science, and data science.