I was able to get an Atari 400 (not XL, sadly) for a firesale price. The problem with all the Atari's in my mind was that they were not dev-friendly machines.

Commodore machines came with a rather hefty serial bound book that introduced you to programming and gave you a memory map of the hardware, important PEEKs and POKEs.

Atari's came with trade secrets.

True, the Atari 8-bits did not come with developer docs and in the early years little information was available. This certainly hurt its initial adoption.

But starting with De Re Atari by Chris Crawford in 1982, a lot of development material became available. Compute! had a great line of books, including Mapping the Atari.

It was shame it took so long for that material to appear because the Atari 8-bit have a rather elegant OS, especially compared to its contemporaries.

> The problem with all the Atari's in my mind was that they were not dev-friendly machines.

That was true in the early days of the 400/800, but by 1982 when the 1200XL was released (a few months ahead of the C64) they'd corrected themselves. The board schematics and assembly source for the ROM was a book you could buy at the dealer, and sources like De Re Atari and Compute Magazine had collated all the relevant details of the handful of ASICs such that people could start playing weird tricks.

It wasn't Woz's Red Book (neither was Commodores documentation), but it told essentially the whole story of the devices down to the MMIO level.

My first Archimedes came with a ring bound user's manual that was, IIRC, about 1/3 a guide to using the Risc OS GUI, and then 2/3 a programming guide to the version of BBC BASIC that shipped with it.

(I remember reading it end to end as a child laid on my parents' bed because the light was better in there than in my room, shortly followed by developing the programming addiction that has stuck with me the rest of my life ;)

It didn't cover arm2 assembly, but my parents bought me an extremely good book that did - and described the chip architecture itself in detail as well.

I only touched a Commodore at a friend's place to play games on it, but it sounds like they also understood hobbyists :D

Only a few friends had Atari computers when I was a kid. The one thing that stuck out to me was it had a Help key but most programs told you to press 'H' or some other key for help instead of the Help key, which makes me wonder if knowledge of how to detect that key wasn't in the manual? Atari owners were passionate about their computers and seemed happy with them but at least in my little town, there just weren't very many of them.