On Call Welcome to an unusual entry in The Register's On Call, where an Amiga mystery is never fully explained after the call for help is issued. Can you solve the mystery?

Today's tale takes us back nearly a quarter century to a small development house, working on programs for the Commodore Amiga in the wake of the former home computer giant's demise.

It was 1996, recalled the reader we'll call "Agnus", Commodore Business Machines had finally gone TITSUP* and "our future was uncertain to say the least".

Back then, the company employed a graphics designer, "Paula". Agnus remembered her as "the proud user of a Commodore Amiga 4000 computer, the top-of-the-range 25MHz 68040 box that probably had something like 12MB of memory."

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For those who missed the excitement of the time (or preferred their late '80s and early '90s machinery to have an Atari ST tinge to them), the Amiga 4000 (and subsequent 4000T) were the pinnacle of the Amiga line. The basic 4000 enjoyed either a Motorola 68EC030 or mighty 68040, and up to 16MB of additional RAM could be added to the 2MB of integrated memory.

Heady stuff. The 4000 was succeeded by the 4000T, which sported a 68060 at one point before the plug was finally pulled once and for all in 1997.

While relatively sophisticated (for the time), the office network would regularly fall over, "usually, we found out later, because the marketing manager had decided to be creative with the network topology in his office, messing up not just for him but everyone else," said Agnus.

Paula and Agnus usually found themselves having to swap disks as the network's toes went skywards once again.

On the day in question, and with the network toasted once more, Paula had more pressing things to do than copy disks for Agnus. UFO: Enemy Unknown wasn't going to play itself after all. She directed Agnus to her machine to copy the required files herself.

Paula's Amiga 4000 enjoyed a mighty 600MB external SCSI device, but when Agnus popped over to find the required file, a number of fatal disk errors peppered the screen.

"Paula, your external drive is buggered," Agnus called.

"Have you got the clock open?" was the response.

"No. Wait, what?"

Eventually Paula left the game and came over: "You've got to open the clock application and put it in the corner of the screen."

"She then proceeded to show me how she would open the standard clock application that comes with the Amiga," explained Agnus, "resize it to a certain size, and move it to the top right-hand side of her desktop."

"Try now."

And, of course, the hard disk worked perfectly and the files were copied.

Naturally, Agnus couldn't leave it like that: "I had to do some scientific research."

"I made the clock slightly smaller. Disk errors."

"Bigger. Disk errors."

"Moved it to the other side of the screen. Disk errors."

"Moved it back to where it was, at approximately the same size. Disk fine."

We can only assume that Paula had a particularly nifty bit of security software running. Or, as Agnus suggested: "Your machine is possessed!"

Being a good co-worker, Agnus offered to kill the evil thing with fire, but Paula insisted she was overreacting to a simple IT issue.

Suspecting that the machine was actually haunted by the spirits of all the Amiga fanbois left howling into the void as the brand met its demise, Agnus vowed never "to set foot near the cursed machine again."

And the mystery? Paula never revealed how the fix for the fault had been arrived at, nor how this seemed to be considered perfectly normal behaviour for a computer, even if it was an Amiga.

"In hindsight," said Agnus, "I suspect the issue was a weird DMA conflict between the DMA-based SCSI controller and the rest of the system with the clock application rendering adjusting the timings just enough for it to work."

Fill the comments with theories or, if this has reminded you of a particular trick you had to patiently explain in order to get a recalcitrant bit of kit working, send an email to the Vultures at On Call.

We're waiting to hear from you. ®

* Total Inability To Save Up Pennies