Intel fires warning shots at Microsoft, says x86 emulation is a patent minefield

It's actually unrelated with Connectix. Connectix is much older, and was killed a long time ago.

Virtual PC for Macs was a full-blown JIT though.

> their warning could backfire if it gives Microsoft one more reason to finally walk away from x86 compatibility

Emulation is an important part of walking away, no? Microsoft cares about backwards compatibility above anything else.

Years ago, I spoke with an attorney with a CS background. He had once worked on a case like this. Sharp guy. He didn't tell me the parties involved, and I didn't ask, though I assume he wouldn't speak openly about it while it was ongoing. I therefore don't know how it turned out. It was many years ago, so I might be remembering wrong. I'm not a lawyer, this is not legal advice (neither mine nor his).

Basically, there are two approaches the plaintiff might take here. The simplest is to cite the doctrine of equivalents[1]. This is basically the notion that if you do the same thing in the same way for the same purpose, then it's the same process, even though you are using digital instructions instead of logic gates. The legal theory here is pretty well settled. The problem is that you'd need to justify that digital instructions are obviously equivalent to logic gates, and a skilled professional would have equated them at the time of the patent's filing.

The other approach is to argue that an emulator actually is a processor, and therefore fits the literal claims of the patent. The explanation for this is pretty well-established: it's literally the Church-Turing Thesis[2]. However, the viability of this argument depends on the language of the patent claims. Also, it's hard enough to explain the C-T Thesis to CS students. My undergrad had an entire 1-credit-equivalent course that basically just covered this and the decidability problem. Explaining it to a judge, who (while likely highly intelligent) probably has no CS background, over the course of litigation is likely to be really hard.

Now, Intel certainly has enough resources to do both of these things (and they may also have precedent to cite, that didn't exist back then or that wasn't relevant to that case). Don't take this as an opinion on any possible result, it's just information such as I remember it.

[1]- https://en.wikipedia.org/wiki/Doctrine_of_equivalents [2]- https://en.wikipedia.org/wiki/Church%E2%80%93Turing_thesis

One patent is https://patents.google.com/patent/US6721866B2 which is for LDDQU and probably would not matter for an emulator. I wonder about https://patents.google.com/patent/US7155601B2/en which is a patent on PSHUFLW/PSHUFHW. I wonder if a CPU instruction in which the only difference is that it operates on different registers is patentable.

There are several existing and excellent x86 emulators floating around. In the open source space, QEMU is quite fantastic and well supported. I'm not surprised at all that Microsoft managed to either develop one in house, or acquire one.

x86 is an old and very well understood architecture at this point. The difficulty thus isn't in writing a working emulator, it's in figuring out which features you can support from a business perspective without treading on still active patents. Microsoft is one of the few companies that can probably absorb a patent fight here and come out on top, and if they succeed, it will counter-intuitively threaten the continued dominance of x86. Once they can release an ARM-based version of Windows that sports backwards compatibility (the primary missing feature that caused Windows RT to fail spectacularly) more mobile machines will be free to use ARM chips, and software developers will have incentives to natively support ARM targets for power efficiency reasons.

Since Intel banks on x86 continuing to be the dominant architecture in the desktop and laptop space, they must feel threatened by this move, so the suit doesn't surprise me. They'll now be fighting an uphill battle. On the one hand, Intel processors are still pretty much king in raw performance, but on the other hand, very few consumers actually need the kind of performance that you can only get on Intel chips anymore. A decent web browser runs on just about anything, so an architecture shift in the consumer space is quite plausible. Some could argue that it's already happened with tablets.