From what I’ve read, AMD is not affected. Just Intel processors which includes ARM.
Only partially true. There are actually two classes of vulnerability that have been identified, code-named ‘Spectre’ and ‘Meltdown’ (I know, it sounds like a James Bond novel!). It appears that only Intel is vulnerable to Meltdown, but processors from a wide range of manufacturers (including AMD) have been demonstrated to be vulnerable to Spectre.