The following message is a courtesy copy of an article that has been posted to bit.listserv.ibm-main,alt.folklore.comptuers as well.
[EMAIL PROTECTED] (Michael Ross) writes: > So far, the only leads I have are that the 3270 card in the XT/370 desktop > mainframe machine did 3277 emulation - but I don't know if it supported > Model 1 mode. Ditto for the 'Appleline' external 3270 box for early Mac & > Lisa machines; again I've heard that supported 3277, but don't know about > Model 1 specifically. the signals on the cable change between 3272/3277/ANR and 3274/3278/DCA (although 3274 supported the attachment of 3277) part of the difference was reducing the manufacturing costs of the terminal, they moved a lot of the electronics that had been in the 3277 "head" back into the controller. there had been some amount of work on modifying 3277 to improve the 3277 human factors ... which were then no longer possible with 3278 (since all the logic was now back in the controller). One of the issues was (because of the fundamental half-duplex) ... if you were typing when the system wrote to the head ... the keyboard would lockup and you needed to hit the reset key. A 3277 keystroke "fifo" was created that would handle the input/output sequencing and hold keystrokes in the buffer to avoid the keyboard lockup. Another was being able to modify the repeat key/delay timing to significantly increase the rate. another aspect was because so much processing had been moved back into the (3274) controller ... that interactions that were nearly instantaneous on 3272/3277 would be around 1/2 second on 3274/3278 ... making .25 second interactive response impossible .... the jokes at the time was that the data entry applications were fairly insensitive to system response and TSO with minimum of 1second response already never saw the difference. misc. past posts http://www.garlic.com/~lynn/2001m.html#17 3270 protocol http://www.garlic.com/~lynn/2001m.html#19 3270 protocol http://www.garlic.com/~lynn/2002k.html#6 IBM 327x terminals and controllers (was Re: Itanium2 power http://www.garlic.com/~lynn/2004e.html#0 were dumb terminals actually so dumb??? http://www.garlic.com/~lynn/2007r.html#10 IBM System/3 & 3277-1 http://www.garlic.com/~lynn/2007t.html#40 Why isn't OMVS command integrated with ISPF? http://www.garlic.com/~lynn/2007t.html#42 What do YOU call the # sign? ---------------------------------------------------------------------- For IBM-MAIN subscribe / signoff / archive access instructions, send email to [EMAIL PROTECTED] with the message: GET IBM-MAIN INFO Search the archives at http://bama.ua.edu/archives/ibm-main.html
