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

Guy Sotomayor ggs at shiresoft.com
Thu Apr 21 17:02:59 CDT 2016

> On Apr 21, 2016, at 2:53 PM, Swift Griggs <swiftgriggs at gmail.com> wrote:
> 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! 
3270 terminals are what are termed CUT terminals (can’t remember what
the acronym means) but were connected to a controller via coax.  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.  This is a *very* abbreviated version of how they

The 3270 emulators that ran on PCs required a 3270 board.  That provided
the connectivity to the terminal controller (something like a 3274 or 3174).
The PC handled all of the screen management and protocol interactions
required by the the 3270 protocol.

Because most of the editing was done locally a mainframe could handle
100’s of interactive terminals without a lot of horsepower since they only
saw interactions when an “attention” key was pressed.

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.

TTFN - Guy

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