A Merrimac Little Christmas

cylinder 2, track …. seek error …

“Twas the night before Christmas, when all on the floor not a capstan was seeking, not even the Dartmoor. Phooey!”

Monica slapped the Formica of the machine’s console. Console was perhaps an over-grand term for the collection of lamps, switches, gauges, and the tele-steno grafted onto the Navy surplus metal desk. The matching chair had somehow survived the operation with its dignity intact. The Merrimac 1150 Console Operator Guide purported to explain each feature of the console. Monica liked most that it was just the right thickness to put on top of the chair seat so she could reach everything. She had re-wired and re-plumbed half the console anyway, so the documentary value of the manual declined by the week.

”OK. From the top.”

She jiggled the complicated tension mechanism on the Dartmoor tape unit next to the console and jogged the spindle back and forth with her hand on top of the reel as if to tousle its hair.

A Dartmoor was really nothing more than a license-built version of the Panhard Cyclobande. The units had been converted from metric to SAE for the US market but the intricate aluminum stampings were made from the original French tooling. Merrimac favored them because of their long association with Panhard. As a practical matter, it was the only electrohydraulic tape unit left on the market when the 1150 was built. Now, this one might be the last of the last.

Monica tapped the little bleed check diaphragm once.

A Dartmoor spool held a hundred meters of slippery Denbridge tape that circulated endlessly in an elaborate cage that looked like a Gran Prix racetrack. When given an address on tape, it returned the answer read from that portion of tape just as it sped by one of reader bars. The unit kept track of the addresses zooming by not by a regular tape counter but by a series of small servo holes that encoded the address alongside the regular holes for data. This servo track fed a complicated regulator assembly that managed the acceleration and deceleration of the tape as it switched its direction automatically to find the requested data.

“Ah.”

What made the Dartmoors unusual was ‘la cadence’. This was the system that adapted the tape speed based on how quickly matches were found. If a program read every value on the tape consecutively, the drive would gradually match its speed to the rate at which the program could accept them. If the program only wanted every tenth value then the tape might move much faster. If the program consumed values completely randomly, it would be hard to guess just how it might behave. Smart programmers could try to get their program to ride the Dartmoor like a mechanical rodeo bull and occasionally request data that they did not need but which might favorably influence the cadence mechanism. In Merrimac circles, this was called Lamminating. Monica Lamm was a very smart programmer.

Monica prised the cover off the side of the unit. She considered the loom of exposed wiring and did a couple of quick mental calculations. With that, she dragged a couple of leads from the console tone generator. She clipped one to the frame, out of her way. The other she clipped to a half-buried terminal labeled ‘HIT’. She turned the dials on the generator and flicked a toggle to engage it. She pressed ‘RUN’ on the console and held it for a few seconds until the oscillator lamp went out. The Dartmoor crept into motion and began to circulate the tape. Less like a Grand Prix car and more like its driver, walking a new road course to get a feel for it.

“Better.”

Monica fiddled with the FREQ knob and the tape holes began to blur a bit as they moved.

“Good! Thank you!”

She put her hand on the cabinet in an encouraging way and the first lead fell off. The drive began accelerating until the safety brake clunked and the drive shuddered to a halt. It had run for only about twenty seconds but that run represented a hundredfold improvement over the last run.

Monica was elated. After looking quickly around the room, she clipped the leads back into place. She slipped off a shoe and removed one of her nylon stockings, wrapping it around the Dartmoor to hold the cover in place. With that loosely held, she stuffed the thinnest Merrimac guide she could reach between the frame and cover to leave space for the lead wires and pulled the stocking snug and tied it with a careful knot. That would do until Nick came in the morning. Nobody would even miss ‘Advanced Programming Concepts for Your New 1150’.

She started the machine up again. This time it ran and kept running. After about a minute, one of the conventional tape units started and soon all eight were running.

“There arose such a clatter!”

Monica leaned back in the console chair and smiled. This was good clatter. This was joyous noise. After three days of downtime, this was the good news she needed.

“Well, it’s a couple of days late I guess, but Christmas finally came.”

Monica studied the flicker of the lamps on the console and decided that the machine was running at about 5 percent of its regular speed. With her change, the drive believed it was finding requested data incredibly quickly and so slowed itself down until it reached the minimum speed.

“Ok. I guess we’re not going to finish overnight. I’ll give you 12 days.”

She reached to pet the Dartmoor, but pulled her hand away at the last moment. It was late. The old drive was working and Monica needed to settle her brain.

Instead, she gave the machine a wink and said “To all a good night!” to the empty machine room. She slipped off her other shoe and padded over to the battered Merrimac Operator’s Cot and was asleep within a minute.