But that defeats the purpose of supporting any extensions at all in the big core that the little core doesn't support. Software will get the lowest common denominator answer and just not use avx2. So why support it in the first place? Why not just do the right thing and have uniform extension support like big.LITTLE?

Currently Intel likes to disable features on some models of Core cores for product segmentation reasons. I'm pretty sure processors sold under the Pentium or Celeron brands already have enough features fused off that they're roughly comparable to the Atoms this is being pared with. You also fuse off things like sections of cache or whole cores that have manufacturing defects.

Chips aren't designed from scratch. They're assembled out of previously designed components and in this case Core cores and Atom cores were never designed to work together.

No - but that just means that Intel shouldn’t do this at all. Either don’t support stuff like avx and avx2 in the big core by disconnecting those blocks or support a slow microcode version of avx and avx2 in the little cores. Supporting different extensions for a CPU used with modern preempting OS’s doesn’t make any sense.

> Either don’t support stuff like avx and avx2 in the big core by disconnecting those blocks

That's partly what they did. From the article: "One thing we can confirm in advance – the Sunny Cove does not appear to be AVX-512 enabled."

Maybe they also fused off AVX & AVX2 support in the Sunny Cove core as well, we'll see.

And disabling AVX in cores that otherwise support it is already a common thing - see the Pentium & Celeron lineups that Intel currently sells. They don't have AVX/AVX2, even though the cores inside them definitely could offer it.