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IBM PCjr won't boot

When it comes to joysticks, didn't Atari have some kind of patent on their design? I know a lot of home computer manufacturers probably ignored that and implemented digital joysticks in the same way, but supposedly IBM was a too big target to do something stupid that could end up in a lawsuit, and whether Atari were willing to license the concept or not, I dunno. After all, IBM PC (and PCjr) were potential competitors to their 400/800 and later 600XL/800XL series.

Anyway, did anyone else other than IBM at that time use a motherboard power connector in the same style as on the original PC and later XT? If not, you could say that design itself was proprietary, non-standard or whatever. If the interface was patented, why couldn't IBM use it on the PCjr as well? Ah, they wanted to separate the professional IBM PC sales from the more home-oriented PCjr sales by making as many components as possible different?
 
It would be hard to believe that Atari had a patent on a digital joystick. There would have been a lot of prior art. Digital (on/off) is good for taking abuse, but doesn't provide anywhere near the information or feedback that an analog joystick provides. Then again, the analog joysticks are a pain because they constantly need to be recalibrated.

The power connectors on the motherboard were probably not a new design either. A lot of what was in the IBM PC was off the shelf parts that you could buy from AMP and similar vendors.

The PCjr had an entirely different design point. Using an external power brick cut down on the heat generated inside of the machine, and thus reduced the cooling requirement. It also cut down on the weight of the machine, which was important considering the plastic case. The brick steps the voltage down to 17VAC, and then an internal card produces the DC outputs.

A PCjr doesn't need a fan unless the floppy drive is installed. In the base configuration, it is a fanless machine.

Also the power supply in the machine is much smaller because it doesn't have space for a hard disk or second floppy drive. Integrated circuitry and lack of expandability meant that the power supply could be tailored exactly to the machine. The original power supply provided just 33 watts, which is very small. An improved power supply put that up to 45. The power supply design with the external brick takes up much less room than the PC or XT power supply, which is built for much bigger loads.

Of course all of this fell apart when people started to expand their machines. With more than 2 sidecars you need to consider adding additional power, via a sidecar of course. And all of the expansion deck products provided their own power supplies too. There was one option (the Cluster Adapter) that was so power hungry that you couldn't even have it on a machine with a floppy drive unless you had a power sidecar added.

Integrated designs are great on paper, but sometimes they fail the reality check. The PCjr failed because people wanted more expansion than the machine was designed for.
 
Re joysticks: Possibly Fairchild Channel-F predated Atari VCS. As far as I know, both systems use the same joystick pinout. It was not that the joystick was digital per se they would have some patent on, but more like the chosen pinout and functionality.
 
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