[TUHS] core

Tim Bradshaw tfb at tfeb.org
Mon Jun 18 19:25:03 AEST 2018

Apropos of the 'my iPhone has more power than our System-360/50, but it has nowhere near the sheer I/O throughput of a mainframe' comment: there's obviously no doubt that devices like phones (and laptops, desktops &c) are I/O-starved compared to serious machines, but comparing the performance of an iPhone and a 360/50 seems to be a matter of choosing how fine the dust you want the 360/50 to be ground into should be.

The 360/50 could, I think, transfer 4 bytes every 2 microseconds to/from main memory, which is 20Mb/s.  I've just measured my iPhone (6): it can do about 36Mb/s ... over WiFi, backed by a 4G cellular connection (this is towards the phone, the other direction is much worse).  Over WiFi with something serious behind it it gets 70-80Mb/s in both directions.  I have no idea what the raw WiFi bandwidth limit is, still less what the raw memory bandwidth is or its bandwidth to 'disk' (ie flash or whatever the storage in the phone is), but the phone has much more bandwidth over a partly wireless network to an endpoint tens or hundreds of miles away than the 360/50 had to main memory.

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