Yep, I was about to reply with similar stuff but yours posted first. So it's the case when PC came out, but now as you said, modern PCs are already clusters of

Yep, I was about to reply with similar stuff but yours posted first. So it's the case when PC came out, but now as you said, modern PCs are already clusters of computers with dedicated functions. The main differences between PC and Mainframe are around: 1. CPU instruction set. 2. Provisions for high availability/reliability and IO at scale.