> That generates an interrupt in the host, and then the host issues a read. > > This kind of approach, where the terminal generates an interrupt for > each key-press, wouldn't be so expensive.
I beg to differ. I/O interrupts on a 390 are *unbelievably* expensive if the amount of data transferred is one byte. A LOT of stuff happens -- everything in the architecture is designed to minimize that happening. You'd have to have a continuously running channel program to make this only painful rather than impossibly so. Cf the history of the original BusTech network adapter and the Lippke driver for it -- the same physical hardware was literally almost 5 times faster if you didn't use the 8232 I/O model but a continuous channel program. > This would require a local controller; perhaps a channel-attached > netvista would do, We'd need a inexpensive channel adapter first. Not simple or easy. We also can do it in software, which would be much more attractive. ---------------------------------------------------------------------- For LINUX-390 subscribe / signoff / archive access instructions, send email to [EMAIL PROTECTED] with the message: INFO LINUX-390 or visit http://www.marist.edu/htbin/wlvindex?LINUX-390
