0

From this post:

A console is generally a terminal in the physical sense that is by some definition the primary terminal directly connected to a machine.

A console must be a piece of hardware physically connected to (or part of) the host.

Console means the keyboard and monitor physically attachements to a computer.

Console - Special type of terminal which is directly connected to Mainframe for the purpose of OS Administration.

When we say "directly connected" or "physically connected", what exactly does that mean? What is our definition of "directly connected" or "physically connected"? Does it mean it is connected to the system bus?

Noob_Guy
  • 203
  • The actual operator's console was typically built into a desk in the computer room. There would also be a bank of switches and lights on the processing unit cabinet, used to select a boot medium, entry point address, etc. Before about 1975, operator consoles were typically teletypes with a paper roll log, and the RS232 cabling and protocol were almost universal, so the I/O for the console was simple. – Paul_Pedant Jun 12 '23 at 09:17

3 Answers3

0

When we talk about mainframes you have physical connection, cables between terminal and mainframe. And it is not connected to system bus but to communication processor. Of course you can have terminal concentrators to connect more than one terminal to the machine like it is explained here.

Romeo Ninov
  • 17,484
0

It depends quite a bit on what mainframe type you are talking about.

For IBM mainframes, there were (haven't used them for quite a while, hence the past tense) locally attached terminals and terminals attached via a cluster controller. The terminals were connected via a coax cable. Burroughs used a CP9500 communication processor, to which RS232 terminals were connected. Tandem had an OSP (Operations Service Processor).

In general: the console is where the system's messages go. These consoles for mainframes are/were in general physical devices, with a screen and a keyboard, or sometimes a printer. They were/are physically connecte to the system using an RS232-cable, a coax cable or something like that.

I have never seen a connection of the console to a system bus, but then, I have not seen all mainframes, and some may have quite an exotic architecture.

Unix at some point stopped sending all the messages to a console, and in stead logged them to a file (/var/adm/console was my first encounter).

Nowadays, for Unix/Linux systems, a console in the old form is gone. To make things worse: the term "console" is now used for a normal terminal-screen, either physical or as a window in X11.

Ljm Dullaart
  • 4,643
0

From the definitions you listed, this one is applicable to modern Linux (and some other Unix) systems, not necessarily to mainframes:

Console means the keyboard and monitor physically attachements to a computer.

The other definitions you listed are more applicable to mainframes.

A connection between a mainframe and its console terminal might be a current loop serial port, a RS-232 (or its longer-range variant) serial port, or some proprietary solution. Having a PC-style GPU, keyboard and mouse be treated as a console is a more recent innovation that came after desktop systems became possible.

A mainframe might have had a dedicated communication processor or some other I/O card that was responsible for connections to terminals; but whatever the implementation, you would find in the mainframe box a number of ports labeled like "console", "terminal #1", "terminal #2" etc... and in order to meaningfully use the mainframe, you would have to plug in at least one terminal to the "console" port. The other terminals were optional, but without the console, you could not use the mainframe.

The "console" port was likely to have some privileges the other terminal connections wouldn't, like access to firmware settings and/or firmware-level debugger. When a Unix system was booted into single user mode for troubleshooting or major reconfiguration, the console would have been the only terminal that was usable in that state. In regular multi-user mode, the console might have had a slightly elevated process priority compared to other terminals, so in case a program was hogging all the CPU time to itself, the system administrator could still use the console to log in and stop it.

Because of this, the console connection was normally hardwired to a terminal in a physically secure location quite close to the mainframe: either in the server room, or maybe in the adjacent system administrator's office. Since it was a direct, hardwired connection, it would be usable even if any network or other input/output device drivers were failing.

telcoM
  • 96,466