MiniDisc did. You could make one (digital) copy but not two.

(I've both played bridge actively and written SIMD code professionally, bridge rules are way simpler. Actually playing good bridge is probably harder.)

From memory, 2505 MB/sec also sounds on the low side for LZ4 on a modern CPU?

Yes. Note that it doesn't need to be someone else's relay; anyone with IPv4 connectivity could easily route 2002::/16 into IPv4-land (without having to announce it in BGP for others to use). You could even announce 2002:aabb:ccdd::/48 as a more-specific in BGP if you wanted, although this was more exotic.

I'm always fascinated by how many people think IPv6 adoption would have gone lightning-fast if we just used This One Weird Trick, where said trick has actually been tried and didn't help. They usually refuse to back down even after you tell them so.

Yes and no. The current internet arguably does not work without a browser and a TLS stack anyway, neither of which is easily implementable (e.g. number of practically usable rendering engines is in the single digits). I mean, I can piece together an IP packet, too, but there's not that many usable services reachable that way.

1. It would have 128-bit addresses. 2. It would have end-to-end encryption (or was it authentication, I forget).

IPv6 was supposed to fix both of these, with IPsec mandatory, but the latter demand sort of faded out into obscurity. We ended up basically solving encryption by pushing everything into TLS anyway, which I guess solved much of the same problems although at a very different layer.

Note that none of this assumes any sort of acceleration from parallelization (be it through GPUs or reusing work across servers) or precomputation relative to what a normal client does. Compute is just really cheap in dollars compared to the cost of having a user wait, and these companies _also_ have a lot of appetite for spending dollars compared to that of a normal user. As others have pointed out, the only reason why Anubis works (sort-of; not for everyone) right now is that it is uncommon enough, essentially “proof that you bothered to have your crawler run JavaScript at all”. It's a confusion measure.

Proof of work does not work.

In general, you must expect to try ten things and then one of them will help you; fewer if your ideas are bad. :-) Occasionally, you learn new things (either about your machine or your language or your code base) and then you can try that elsewhere in the code (but don't go overboard, every technique has its limits).

DO NOT FALL PREY TO SUPERSTITION. Always measure in one way or the other. Don't do stuff blindly just because someone on the Internet told you (there's a _lot_ of bad performance advice out there).