https://www.jpl.nasa.gov/news/press_kits/mars_2020/landing/m...
> Just like Curiosity, Perseverance has two main computers, or “brains”: One is active at any given time, while the other serves as a backup. Both use radiation-hardened RAD750 computers, and together, they’re referred to as Rover Compute Element A and B.
> Another RAD750 serves as a third “brain,” on Perseverance. Called the Vision Compute Element, it is equipped with a special card for analyzing images. This card has a Virtex-5 field programmable gate array (FPGA) and is the driving force behind Terrain-Relative Navigation and the Lander Vision System, which analyzes images of the landing site during descent and compares them to an onboard map to determine the rover’s position relative to the ground.
That "Virtex-5 FPGA" is an interesting one too...
https://www.xilinx.com/products/silicon-devices/fpga/virtex-...
Where it is listed as "Space-grade Virtex-5QV FPGA"
if it was a good idea to have multiple redundant CPUs on these spacecraft, the spacecraft would have multiple redundant CPUs.