AFAICT[1] the latest generation of SpaceX Starlink satellites use AMD Versal XQR SoCs, which are built on a 7nm process with components like the main processor (dual-core ARM Cortex A-72) and memory (DDR4) clocked in the gigahertz, not megahertz, range.[2] At least some of these SoCs models (presumably the lower-clocked ones) are certified for geosynchronous orbits, not just low-earth orbits.

[1] https://www.pcmag.com/news/amd-chips-are-powering-newest-sta...

[2] https://docs.amd.com/r/en-US/ds955-xqr-versal-ai-edge/Genera...

What is the designed lifespan of a Starlink satellite?

Just to put in my 2 cents as someone tangential and sometimes a little too close for comfort for the field: with FPGAs (aka the half of this SoC doing the real work) there's often a lot of work that goes into radiation tolerance and hardening which are different things. It's not like you can just put the chip in space and be done. You have to do things like scrubbing the "bitstream" regularly for errors, triple-module-redundancy (aka cut yourself to 1/3rd of the chip's capacity), and other stuff.