Storys from the NCR 615 Century Field Engineers

[heikobuss]

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
Heiko

[heikobuss]

Hello,

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
Heiko

[heikobuss]

Hello,

I can't believe it - is there really not one Century Field Engineer all over the world able to tell us some storys from his daily work on the customers site?

Heiko

[lapham]

I wasn't a century FE but worked in the Chicago Data Center where they had 2 Century 300's. I mainly took care of the phone line problems as they were on-line to banks in 8 states. I was 605 trained so also did the 621.s and 721's. I unstuck many CRAM units and dabbled/helped on other units. It was a big deal the day they installed a one meg memory unit - the size of 2 refrigerators. Compare that today  to a cell phone - cell has probably 100 times the computing power.

[heikobuss]

Hello lapham,

thanks for your post.

>> I unstuck many CRAM units

Did they in the Chicago Data Center ran a 315 System parallel to the two Century 300, or - I can't really believe it - did they connect the CRAMs to the Century?

>>It was a big deal the day they installed a one meg memory unit

Yes, the 16k Rod Memory Modules for the Century were really big and heavy. I serviced some Century-100 with two modules installed. But (in Germany) on Century-200 with more than 32k we used a memory from Memorex? EMC? in a 19 inch cage - really small compared with the rod memory module. I don't really remember why, but timing problems could be the reason.

I searched intensively in the Net for a picture from the 16k Century rod module, but could'nt find any.

Greetings
Heiko

[lapham]

The CRAM units were on the 315's they also had.  There were rod memory cards, but I don't have a picture of one. I have many pictures of the data center (10)but haven't figured out how to post them on here. If you provide me with an email  (message me) I could sent them to you.

[wally]

Here you'll find more on the 315 rod memory.

https://www.semanticscholar.org/paper/A-Thin-Film-Rod-Memory-for-the-NCR-315-RMC-Computer-Higashi/b19a69abd207e2c4ef0acd8ec7e727d94a672e25

and here is a PDF on it
http://www.thecorememory.com/NCR_Higashi.pdf

Neither did I find anything on the 16k rod memory for the Century.

Regards Wally.

[Aleksandrs Guba]

Hi Lapham,

The mailbox to send any related photos: webmaster@thecorememory.com

Regards,
Aleksandrs Guba
Webmaster


P.S. Attached images provided by Rich Lapham!

[Aleksandrs Guba]

Attached images provided by Rich Lapham!