Historically, it hasn&#x27;t really taken &quot;serious competition&quot; to invite threats. There&#x27;s a reason that the best-known open-source ARM implementation explicitly only targets ARMv2 (which dates from the days when the &quot;A&quot; stood for &quot;Acorn&quot;) [1].<p>That said, people who just want to play with ARM-based hardware can get pretty far by leaning on the GNU support and third-party documentation (there are some Game Boy Advance documents that cover the ARMv4 instruction set, for example).<p>[1]: <a href="http:&#x2F;&#x2F;opencores.org&#x2F;project,amber" rel="nofollow">http:&#x2F;&#x2F;opencores.org&#x2F;project,amber</a>