Comment by userbinator

A lot of the non-mainstream PC clones, especially in non-conventional formfactors, were more subtly different than those of major manufacturers like Compaq, and probably lacked the testing required to uncover bugs like this. I'm guessing the BIOS implemented the A20 enable call so it returned success, but all it did was send a command to a nonexistent keyboard controller (especially on a PC laptop, not having an 8042 is a bad idea since the 8042 emulation is usually built-in to the EC and interfacing with it is far easier than requiring a whole USB stack, but I digress...) The OEM bought the BIOS and didn't customise it completely to the particular system's setup.

Things might've been better if the PC had been officially standardised, since AFAIK despite IBM publishing schematics and BIOS source code for everything up to the AT, other companies couldn't make use of that and still had to reverse-engineer the functionality.

I see a lot of people, mostly newcomers, complain about the "legacy" stuff but keep in mind that the strong backwards-compatibility is what made the PC platform as successful as it is. It has its quirks due to evolution, but the relative openness and stability of the design is why I'd still prefer it over some of the other platforms out there e.g. ARM SoCs where everything except the CPU cores vary widely between manufacturers and models. To me, a mostly openly-documented platform is far better than a proprietary one even if the latter is "legacy free".