On 2016-04-21 6:53 PM, Swift Griggs 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 ?
The cards handled the communication protocol between the control unit
and the terminal as well as having the appropriate line driver and
receiver. The 3270 system used coax, I think you are thinking of 5250
emulation when you mention twinax. 5250 emulation was used to to
connect to SS/34, S/36, S/38 and As/400. The 3270 or 5250 emulation
card is just the adapter card that is appropriate for the connection
just like you would use a RS-232 adapter to emulate a VT100, but these
cards also handle all of the protocol where as for most serial terminal
emulation most of the protocol would be handled by software. There was
also 3270 terminal emulation that connected via a BiSync or SDLC adapter
card as well. Yes I understand "a while ago" it has been at least 20
years since I have seen any of these machines. Yes the extra keys on
the extra keys on the keyboard gave you a layout much like the later
3270 system keyboards, but not like the 3275,6,7,8, and 9 which had
considerably fewer keys. The display was also a high quality display
and it was likely attached to a special display adapter, since it could
support the 3270 system vector graphics, but I don't recall what the
used for display adapters.
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!
Yeah me too now after supporting UNIX system for more than 25 years, but
I am more a hardware person than software, but I started out fixing 3270
terminals as well as other IBM terminal products that connected to
mainframes.
-Swift
Paul.
