Well, it is actually extremely expensive to produce customer-facing documentation of high quality. Vendors don't do that (or do to a limited extent), because a) this is big cost and time consumption, and b) because the makers don't request it anymore; even given such information of high quality they would not use it! Many of them have acquired the reflex of calling vendor's support for even the smallest question (let alone anything involved -- they will shift that job to vendor entirely), so the vendors have performed the selection of customers they can work with that way, and neglected the others (and the documentation).

From personal experience, the expectation of good documentation today for many developers -- an instant reply to a question limited to 140 characters.

The information is available just not to a larger group of people.

Opening up stuff in hardware is just miles behind software. That's all. Also a lot in open source software is driven by people that realize the benefits from both an engineering and a marketing perspective. The gap between these skills is even wider in hardware.

Not arguing with you, but first thing in the way of opening up hardware, is vendor's liability. It is very hard to communicate to a customer who had just spent money on a big run of boards, only to discover uncorrectable flaws in the SoC, that "we actually imply no warranty and no fitness for any purpose". If this liability question could somehow be solved, the remaining progress on opening up would be made much faster.

Couple this with a very real fear of accidentally giving away the secret sauce of the chip, and you have a most potent potion of paranoia.

Most Microprocessor manufacturers Atmel, Microchip, ST, TI, NXP etc give out incredible documentation for free and probably enough though for a competitor to reverse engineer a dodgy but functional implementation of the chip (say in a FPGA).

Not sure why these guys go all the way where as companies like broadcom do not, I would put it more to shaving the last cent off the chip. I know which ones I would choose as an engineer but you dont often get to make the choice.

Considering that automotive fault tolerance is one of NXP's core competences, I can guarantee you that there is plenty of secret sauce that you're not privy to in those chips.

That being said, your point is well taken.

I suspect it prevents potential customers from realising that their competitors' chips are better and have actual documentation until it is too late.

Not a really satisfying answer but I've been told it is to prevent competitors from reverse engineering.

Yeah, probably you're right. And it's not like it would stop the really determined guys - X-Raying stuff would do a part of the trick, and maybe stealing the documentation would the other part.

Some fraction of the potential customers will call you, which gives you contact information. If you're proactive enough and good enough at selling to that fraction, the end result is beneficial for you.

I'd love to know whether that works...