Article mentions two reasons: it's a proven design that is reliable. And it has been radiation hardened: > Mars’ atmosphere offers far less protection from ha

Article mentions two reasons: it's a proven design that is reliable. And it has been radiation hardened: > Mars’ atmosphere offers far less protection from harmful radiation and charged particles than Earth’s atmosphere. A bad burst of radiation can badly wreck the sensitive electronics of a modern processor — and the more complex the chip, the more can go wrong. Plus, at 138 million miles away, it’s not like NASA can just swap out the processor if things go sideways. > To make the system even more durable, the PowerPC 750 chip in Perseverance is a little different than the one in the old iMacs. It’s technically a RAD750 chip, a special variant that’s hardened against radiation and costs upwards of $200,000