"Twinax Connectivity in the 21st Century"

by Martin Pladgeman (March 2002)

For the last fifteen years IBM midrange host computers have been accessed using a proprietary cabling system called Twinax. This type of cable has two inner cores, (transmit and receive) plus an outer shield.

Twinax cable can support up to seven devices in a daisy chain formation.

These days many users are looking for ways to replace this type of cable with twisted pair (cat 5). Most new installations are wired using this more flexible type of cabling system. Twisted pair can be used to support Twinax terminals and printers with the use of Active and Passive star hubs at one end, and Twinax baluns at the other.

This type of star formation permits only one device per cable, however unlike the Twinax cable, a device can be added and taken away without affecting the other devices on the same port.

Terminals

"Terminals are on the way out" - that what I was told in 1982, when I first started servicing dumb terminals. "PC's will supplant them, they are inexpensive to buy and can perform many more tasks", or "Thin Clients will be the new revolution", were the messages IBM was preaching in the early nineties. IBM has recently pulled out of the Thin Client business due to lack of sales volume. Dumb Twinax Terminals, however, are still selling strong. Applications that run on the AS/400 require only a Terminal to be able to function. If the task is order entry, accounting or any other type of AS/400 application, giving the user the extra capabilities of a PC or Windows-based Terminal does not increase productivity. It gives the user something else to play with, something else to go wrong, and requires the learning of new skills to manage either the PC desktops or "Fat Servers" (for the Thin Clients). Many companies have discovered (to their dismay) that changing the user environment has resulted in substantially less productivity. What appeared to be great value for money has turned out to be an expensive mistake.

Internet

Many companies are making use of the public Internet to link their branch offices. This type of communications can save thousands of dollars a year. But what can be done with the Twinax devices when such a move is contemplated?

Option 1

Do nothing, the Internet is a scary place, you don't want to mess with it.

Option 2

Throw away all your Twinax devices and switch to IP-based Terminals or PC's.

Option 3

Replace your old SNA Twinax Controller with a Twinax controller that uses only TCP/IP.

Option 1

While this is probably the most expensive option, it is also the most common. Most users think of the Internet as a very slow network with lots of potential dangers. They remember logging on to Microsoft.com and waiting for the screen to finish downloading (the Web page contains 200K worth of graphics, and it is likely that at the same time, thousands of other users are doing the same thing). What these users don't realize is that 5250 traffic requires very little bandwidth, since there are no graphics! A Dumb Terminal with an entire screen filled with characters requires 2K of bandwidth when the Enter key is pressed. In our experience, when users move to the Internet for 5250 traffic, they see an increase in performance. TCP/IP-based controllers typically cut the response time from over two seconds to well under a second. This is due to the way the AS/400 deals with SNA vs TCP/IP.

Option 2

This is a popular option. PC's and Thin Client terminal sales are on the rise. They do, however, have extra hidden costs. Any TCP/IP device requires an address. The more devices, the more complex the addressing scheme becomes. Thin Clients require Fat Servers, which are expensive. Managing a Citrix or Terminal Server environment is a far cry from switching on a Twinax device and deciding which address to give it (0-6). What about software costs, keeping current with new OS releases, hard disk crashes, and virus detection? Ever heard that if you get a Thin Client you will never need to add memory or replace the processor? Then why has IBM made so many different models since the first 386 versions were released, to the latest Pentium 3's?!

Option 3

Better On-line Solutions is the only company that has produced a true, pure TCP/IP controller. It requires only one IP address - no matter how many dumb devices it supports. It can connect to multiple AS/400s. Configuration can be done via a Web browser using simple HTML pages, or a dumb terminal. You can install this device in less than ten minutes. As it has no SNA timing related issues, such as those seen with AnyNet (a.k.a. MPTN), it works fine over slow and problematic WAN's (like the Internet).
Is there any doubt that BOS' e-Twin@x Controller is the right solution for your organization?