NCR Computers of the 20th Century => Mainframes => Topic started by: heikobuss on August 30, 2015, 06:22:24 pm

Title: Storys from the NCR 615 Century Field Engineers
Post by: heikobuss on August 30, 2015, 06:22:24 pm

Hello to all,

I open this thread to invite all the former Century Field Engineers around the world.

Let's talk about the hardware of this nice machine - the last NCR-Mainframe where Field Engineers are trained on very extensiv, very close, very long and down to chip level. The next mainframe-generation training just goes mainly down to board level (board swapping).

Let's talk about the internals and architecture of the Century processor and the peripherals. Let's tell all the interesting, sometimes exciting or funny stories we experienced at the customers site during fault finding and repair!

I remember the LA- and LB-Registers. I remember stepping throug N-Flows and P-Counts via the Microstep-Switch on the Console.
I remember in the processor the K1-Latch - the "miscellaneous decision latch"! This latch was driven by really a lot important Terms!

When processing an I/O-Command (hex "70") I remember the trunk terms "JCSEL" and "JCSIP" (and others) and the PAF and the "control words" (hex 04xx).

I remember the  "Between-commands-testing" (BCT) after each processed command.

I remember loading the Bootstrap Card into the Address "00A0", "ACT", "LOAD" - and things began to move ....

And - of course - I remember the head crashes on the 655 Disk - then cleaning everything,changing the head, mounting the alignment pack, aligning the heads ....

The 657 Disk has really rare head problems - but the Actuator was oil-driven - and sometimes the diaphragm breaks ....

657 Disk: I remember installing the PERK-Feature on a century 200 - this speeds up the trunk to operate the 657 in high density mode (1322 Bytes/sector). What a lot of wirewrap work ....

And, and, and ...

Please join and tell all the storys from your work at the front!

Kind regards

Title: Re: Storys from the NCR 615 Century Field Engineers
Post by: heikobuss on October 11, 2015, 01:10:22 am

a collegue from NCR Hamburg (Germany) had to fix a funny fault on a Century-100.

Everytime when a Program selects the Magtape, the ME-Light (Memory-Error) on the Console turns on, and the System stops.

You remember: When executing an INOUT-Command, the A-Adress of the Command points to the PAF-Characters needed.

The Trunk/IO-Logic then sends all the needed PAF-Characters (Trunk/Position, Function, etc.) to the Peripheral. When all necessary Characters are send, the Peripheral (or, in this case, the Magtape-Controller) raises the "End-of-Control-Information"-Line on the trunk, and the IO-Function starts.

But the Controller failed to raise this line, and so many PAF-Characters where send to the Controller until the "end of memory" in the processor was reached, and the "LGM"-Term ("L-Register greater memory") was raised, and the ME-Light on the Console  turns on ....

The reason was a faulty NCR80-Chip in the Magtape-Controller. My collegue hat to replace this chip, and everybody was happy .....

Fascinating memorys - that was the time you had to know what to do!

All the best