Would guess "cosmic rays". Sun Microsystems had a batch of UltraSparc servers that were very sensitive to it, and it was a big issue. https://docs.oracle.com/

Would guess "cosmic rays". Sun Microsystems had a batch of UltraSparc servers that were very sensitive to it, and it was a big issue. https://docs.oracle.com/cd/E19095-01/sf4810.srvr/816-5053-10/816-5053-10.pdf https://docs.oracle.com/cd/E19095-01/sf4810.srvr/816-5053-10... https://en.wikipedia.org/wiki/Cosmic_ray https://en.wikipedia.org/wiki/Cosmic_ray