gmark@ihlpf.ATT.COM (Stewart) (03/18/88)
Has anyone out there had any experience with the SSI 3270 SNA terminal emulator for the UNIX-PC? I've only used this type of teminal at IBM where it was of course hooked up to a non-UNIX system (years ago). The speed was phenomenal, but not liking the system a heck of a lot, I didn't pay too much attention to it otherwise. Is the apparent speed a characteristic of the terminal? How the heck could a 7300 emulator keep up with that (any ideas, Mr. Fox?)? Has anyone used the emulator? Is it usable for anything resembling UNIX? How well does it work? Why is it so darn expensive? G. Mark Stewart ATT-BTL Naperville, ix1g266 ixlpq!gms 979-0914
alex@umbc3.UMD.EDU (Alex S. Crain) (03/19/88)
In article <4037@ihlpf.ATT.COM> gmark@ihlpf.ATT.COM (Stewart) writes: > >Has anyone out there had any experience with the SSI 3270 SNA >terminal emulator for the UNIX-PC? I've only used this type of >teminal at IBM where it was of course hooked up to a non-UNIX >system (years ago). The speed was phenomenal, but not liking the >system a heck of a lot, I didn't pay too much attention to it otherwise. If you had looked at the back of your IBM terminal, you would have seen that it is connected with coax cable and DNC connectors, not the telephone wire that ascii terminals use. The way IBM terminals work is that the terminal knows what the screen looks like, and when the screen is supposed to change, the computer sends the changes to the terminal, the terminal decodes the changes, and the terminal fixes the screen. This is extreamly fast, because the terminal does most of the work. the terminal also buffers the input, sending input a line at a time to the mainframe. The advantages to SNA are: Its REAL fast, sort of like putting your vt100 on the ethernet. The terminal server can use a network protocol, allowing zillions of terminals on the same system. Since many I/O functions take place in the terminal, The I/O overhead of the processor is reduced. The disadvantages are: No character at a time input. Because of the input buffering, all input is held until the ENTER key is pressed. Thats whe XEDIT (The stock IBM editor) is so weird. Also, No EMACS. It only works on an SNA network. And SNA networks are usually only IBM mainframes. Its expensive. Roughly equivelent to a slow ethernet card. Which is roughly what it is. -- :alex. nerwin!alex@umbc3.umd.edu alex@umbc3.umd.edu