I sent this message to Mike Magee of The Inquirer this morning:
Hi Mike,

I’m a freelance author, with one book published by O’Reilly to my credit and a few appearances in Computer Shopper UK.

I visited the Scott Mueller link you referenced at http://www.theinquirer.net/15040206.htm, and just to alert you, I’m not certain that Scott Mueller’s dates on the Dell systems are correct. In late 1998, I attempted to upgrade a Dell P133-based system with an AOpen AX59Pro motherboard, in order to get around the nasty memory limitations in Intel’s 430VX chipset. I knew the motherboard worked because I pulled it out of another working system. The board didn’t work in the Dell. Then, when I reinstalled it in the system I pulled it from, it didn’t work there either.

Fortunately I didn’t kill the power supply so I was able to get the system up and running again by replacing the factory board.

This leads me to believe that Dell has engaged in the practice of nonstandard wiring since 1996.

My recommendation to my readers has always been to replace the power supply when replacing a motherboard in a Dell, since standard ATX power supplies easily bolt into the Dell cases. Any brand-name power supply purchased at retail (Sparkle, Antec, Enermax, etc.) is likely to be of higher quality than the stock Dell power supply anyway, but that’s an additional upgrade expense people may not consider.

I suspect the reason this hasn’t been more widely known is that Dell mostly sells to corporations and has only recently gone after the consumer market in aggressive fashion, and corporations rarely replace motherboards. The labor involved in making the swap, then reinstalling the operating system and applications, costs too much. There’s less labor involved in replacing the system, and then you have a system covered under warranty.

Incidentally, while Gateway does use the standard ATX pinout, many Gateway cases use an odd-shaped power supply. So while an aftermarket power supply will function electrically, it’ll take some cutting and drilling on the case to allow you to bolt it in. Most people will prefer to just buy a new case if the power supply in their Gateway dies–and the power supply is usually the first component to go in a Gateway, in my experience.