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One of the reason they still exist is that a software written and compiled in late 80s is still running in production environment unchanged since then. They al
by vb-8448 3y ago
One of the reason they still exist is that a software written and compiled in late 80s is still running in production environment unchanged since then.
They also have some other cool features like "serverless", low operational overhead, decoupling between cpu and storage.
- shiroiuma 3y agoI thought the big thing was redundancy and correctness, like having 3 processors run every computation and voting, to make sure no one's bank balance is accidentally in error.
- vb-8448 3y agoI don't think most of the programmers or managers knows about this, they just assume computation is right; and for sure the correctness check of the bank balance is done on the application level.
- guenthert 3y agoWell, if it were only to run software written in the 80s, an emulator would do (modern hardware compensating the inefficient execution many times over).
- vb-8448 3y agoI'm not sure, but I guess under the hood IBM does some emulation to guarantee backward compatibility.
- thequux 3y agoLargely no, actually; modern z/Architecture is a strict superset of the System/360 ISA from the 70's. Every instruction that accesses memory has the original 24-bit address version, a 32-bit version, and a 64-bit version that also uses 64-bit registers. Thus there's no emulation involved; at least, not that's visible to the OS (but who knows what the microcode is doing underneath)
- Pet_Ant 3y ago> modern hardware compensating the inefficient execution many times over That's assuming volumes haven't changed. They had credit cards in 1980 but the volumes have gone up considerably. I'd also guess trading volumes and other financial products as well.