High performance coprocessor boards of the 80s and 90s - was Re: SGI ONYX

[Swift Griggs]

On Thu, 21 Apr 2016, Paul Berger wrote:
> No the 3270 PC and 3270 AT where a special configuration for 3270 terminal
> emulation it conatined a special keyboard with more keys that the normal
> keyboard and connected to a special adapter card in the system.

I never understood the dynamics of 3720 emulation.  Was it *just* a terminal
emulation protocol ala vt100 ?  The main thing that confused me was the
existence of these emulation cards that folks are mentioning.  I remember
seeing "3270 boards" (as folks in the know gestured at them).  They appeared
to run on some kind of twinax, IIRC (been a while and I was probably 14
years old).  Were these extra keys on the keyboard the cruxt of the issue ? 
ie..  the card was there so you could use a "real" 3270 keyboard ?

Why did folks install those boards just to run "3720 emulation" ? Couldn't
they have just bought something like Reflections and done it all in
software ? Can someone school me and tell me what I'm missing about these
boards or 3270 in general. I know little of IBM mainframes, obviously. I'm a
Unix zealot, so that figures, but I'm still curious about them. Thanks! 

-Swift