Comment by rbanffy
10 hours ago
Even though their CPUs are insanely fast, the real power of mainframes is in their IO. The amount of data you can push through those machines is absolutely mind blowing.
10 hours ago
Even though their CPUs are insanely fast, the real power of mainframes is in their IO. The amount of data you can push through those machines is absolutely mind blowing.
Historically this was because each I/O "channel" was a separate computer that handled the actual communication with the device, be it a terminal, disk, tape drive, card reader, printer, etc. and exchange data with the CPU via DMA. This allowed mainframe CPUs, which in the past weren't particularly fast, to handle huge workloads involving hundreds or thousands of users. These days, even commodity computers get blazing fast I/O to bus mastering devices. Where the mainframes win today is on reliability, built-in redundancy, hot-pluggability and expandability of components (you can just plug in CPUs, memory, disks, and network interfaces as long as you can afford them with the machine still running), and service and support. (Mainframes phone home immediately if they detect problems and an IBM service person will be on site the same day to fix it.)