The 386 assembler is terrible

[davidgiven]

It doesn't behave like 'normal' assemblers. For example:

• ax, bx, cx etc are synonyms for eax, ebx, ecx etc based on the 16 or 32 bit mode
• segment and size prefixes must be specified manually via cseg, dseg, o16, o32 etc rather than inferred from the size of the registers
• likewise, instructions which change behaviour according to mode are generated incorrectly if you use the wrong name for the mode (like cwd and friends)
• it's very easy to generate invalid instructions --- invalid configurations aren't checked for

I suspect the 32-bitness was a added as a quick hack on top of the 16-bit assembler. But it's painful to use and really needs to be rewritten.