<story><title>AMD Threadripper 3970X under heavy AVX2 load: Defective by design?</title><url>https://forum.level1techs.com/t/amd-threadripper-3970x-under-heavy-avx2-load-defective-by-design/153883</url></story><parent_chain></parent_chain><comment><author>bdd</author><text>“Unable to perform AVX2 instructions correctly under heavy load” is also a common “WTF Intel!?”–inducing phenomenon. I’m certain SREs who work at companies with more than 1 million servers have a bunch of hair pulling stories.&lt;p&gt;Most (all?) Intel server CPUs in fact decrease clock speed when executing AVX2 (and some other) instructions to keep things a bit more sane. Vlad from Cloudflare wrote about this, more specific to AVX-512 back in 2017: &lt;a href=&quot;https:&amp;#x2F;&amp;#x2F;blog.cloudflare.com&amp;#x2F;on-the-dangers-of-intels-frequency-scaling&amp;#x2F;&quot; rel=&quot;nofollow&quot;&gt;https:&amp;#x2F;&amp;#x2F;blog.cloudflare.com&amp;#x2F;on-the-dangers-of-intels-frequen...&lt;/a&gt;&lt;p&gt;Then there is PROCHOT signal. Which is supposed to protect the CPU from getting too hot but keeps getting raised in lopsided AVX2 loads not because CPU is too hot but voltage regulation gets whacked.&lt;p&gt;You may wonder: what is an example of AVX2 heavy load. RSA multiplication is a good candidate. AES constructions or modes (CBC with SHA, GCM) are implemented in AVX2-BMI2 as well.</text></comment>
<story><title>AMD Threadripper 3970X under heavy AVX2 load: Defective by design?</title><url>https://forum.level1techs.com/t/amd-threadripper-3970x-under-heavy-avx2-load-defective-by-design/153883</url></story><parent_chain></parent_chain><comment><author>ntauthority</author><text>My 3970X on the ASRock Taichi (with default settings, generally) does not seem to reproduce this issue at this time - the system remains operational despite the FMA3 path being used (I&amp;#x27;m assuming this is behind the AVX2 flag? disabling FMA3 leads to a plain AVX path) while running an all-core test with 16K FFTs in Prime95.&lt;p&gt;Either a slight background workload (Windows seems to be trying to use half a core for an OS update) resolves this, or this board does not have a broken power design?</text></comment>