Comment by dojopico
6 days ago
I did VOS and database performance stuff at Stratus from 1989-95. Stratus was the hardware fault tolerant company. Tandem, our arch rivals, did software fault tolerance. Our architecture was “pair and spare”. Each board had redundant everything and was paired with a second board. Every pin out was compared on every tick. Boards that could not reset called home. The switch from Motorola 68K to Intel was a nightmare for the hardware group because some instructions had unused pins that could float.
> Stratus was the hardware fault tolerant company. Tandem, our arch rivals, did software fault tolerance. Our architecture was “pair and spare”.
To expand on this, when Tandem switched MIPS from their proprietary processors, the CPUs were duplicated on a board and compared, and if they disagreed, the logical CPU would halt, similar to Stratus. The software-pair backup processes in a different logical CPU would then take over.