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

[Swift Griggs]

On Thu, 21 Apr 2016, Guy Sotomayor wrote:

> 3270 terminals are what are termed CUT terminals (can?t remember what the
> acronym means) but were connected to a controller via coax.

Ah okay. Someone told me that the voltage on those was enough to feel/shock
you. Was that true, or just a myth ?

> The terminals are ?page mode?.  Basically all of the editing on the screen
> is done locally and then when an ?attention?  key is pressed the
> controller can request the contents of the screen.

Ah, so there was some electrical signaling going on to the terminal
controller and that couldn't be done in sofware, if I'm understanding you
correctly.  Hmm, considering all the limitations at the time, it's seems
like that whole 'buffer <-> forward <-> update' mechanism isn't a bad idea.

> With the advent of TCP/IP on the 370/390/zSeries machines (both HW and SW)
> most physical 3270 terminals have gone away to be replaced by TN3270.

Ah, okay and this is where software emulation became an option, I take it. 
I had to look up the "TN" part, I didn't find anything solid, but from 
some Wikipedia chatter I take it to mean "TelNet". Also guessing they 
created some out-of-band channel to send all the stuff that used to rely 
on electrical signaling.

Thanks a lot for taking the time to explain that. 

-Swift