3 ms·

Main-frame specialty is crazy IO, I'm told, not raw muscle

• jcrawfordor 10y ago
  Yes, the number of instructions per 'business operation' in a mainframe is typically much, much smaller than on something like an x86. This dates back to IBM's early habit of implementing all instructions in lengthy microcode, resulting in instructions that were relatively slow to execute but did complex things, typically taking an entire high level operation (e.g. sum all these numbers) and making it one instruction. A big part of making this happen is the IO model on mainframes which is much more integrated than x86 professionals are used to. In general files on mainframes are not binary blobs but schema-compliant tables similar to an RDBMS, a fact that is leveraged at a very low level when programming for mainframes. This leads to a very different kind of thinking from using microcomputers. I highly recommend that anyone in computing learn to use a mainframe or at least minicomputer operating system, which is affordable thanks to services like PUB400 from RZKH which provides free access to an IBM i minicomputer. Yes, these systems are uncommon today outside of certain specific market verticals (e.g. finance), but the exercise will show you a very different way of organizing a computer system that might help you think outside of the *nix-style box.