Yup, a large portion of hardware design is based on getting below a required maximum failure rate. For metastability, you just keep adding more flip-flops. BTW,

Yup, a large portion of hardware design is based on getting below a required maximum failure rate. For metastability, you just keep adding more flip-flops. BTW, the cache invalidation request may be due to this. They figured they could more easily reach their time between failure interval if they could discount time during S1.