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Two boards for one Console

10/26/2009

I haven't find a clean, elegant solution to the problem I had with the Console, until now (a few minutes ago). The problem is this:

The Console is a "controller", actually the "ultimate resource" when things go wrong with the computer circuitry. But the Console is not just a bunch of lamps and switches but logic as well so it takes board space (more than I expected) and, what is worse, it takes a lot of pins.

I were conceiving a "Console Board" to allocate such logic, but this board would not attach to the Backplane but to the "Master Controller Card" which in turn plugs to two slots (Data and Control) being the only card in the CPU with such a privilege. The Console needs signals from both Data and Control slots hence the need for been connected to the Master Controller Card.

This arrangement never pleased me but no better idea had came to my mind. The worst part is the large amount of interconnections between the Master Controller and the "Console Board", made with ribbon cables plugged to header connectors (something that I truly heat!)... By the way, all this is still on paper, nothing has been built yet.

And, yes, fortune smiled to me just a few minutes ago when I came with a different approach which is this: No one but two Console boards.

One is called the "Console Monitor Board" and it plugs to a Data Slot just as Registers cards do. This cards is responsible for collecting and buffering data from the buses (D-BUS, A-BUS and "Lamps Bus") just to be presented on the Console's lamps (LEDs). It also contains the Entry Switches Register.

The other card is called the "Console Controller Board" and plugs to a Control Slot just as other controllers (such as IDS and the Interrupt Controller) do. It contains the Console's logic and rises internal control signals in the same fashion other controllers do.

So there is nothing special with "console boards"; they are regular "data" and "controller" cards and they follow exactly the same rules. This solution will simplify wiring and will allows me to allocated the different Console's circuits in a comfortable manner.

I think this solution is elegant, but what makes me really happy is to see how the overal design is guiding my mind to every specific solution in a natural way, so it makes me to conclude that the design is, indeed, an elegant one.