Does x86 exclusivity eventually expire?

[Blazkowicz]

I was just thinking that the Pentium Pro is now 17 year old, and patents may expire definitively after 17 years. But rules have been varying, I think it was 20 years from filing date then 17 years after acceptance date.

So, I wonder if the patents on Pentium Pro expire soon, thus meaning anyone could implement an i686 with PAE processor (still missing on MMX, then SSE etc.)
Would a CPU instruction set be protected by copyright? That would be ridiculous so I don't think so.

What would be the timeline for Pentium Pro, Pentium II, Pentium 3 features expiring? A Pentium 3 still can run pretty much anything, barring Windows 8 which requires the NX bit.

I thought it would be funny if someone came up with a $50 "computer on a stick" with at least 1GB memory (perhaps slightly bigger to make room for a heatsink), but able to run Windows 7 or XP or an x86 linux distro.

I think you're free to make a 80486 clone if you wish, and there are quite many embedded 486 clones (SX or DX) but the 486 was actually licensed quite a lot I think.

 

[Ethatron]

You're sure the schematics are publicly available? If not, good luck reverse engineering the silicon. That is if you don't want to "work" on efficient silicon for the x86/x64 ISA from scratch, which is quite a mammoth task.

 

[Blazkowicz]

My question is more about the legal aspects.
Reverse engineering seems pointless but building your own, there were Cyrix, Nexgen, Transmeta, Centaur, Rise achieving that - though often achieving i586 or even i486 compliance only.

Of course you'd have trouble competing with an Atom, a VIA or a Jaguar and "good luck with that" is a receivable answer but I thought, what about something nominally usable like e.g. Xcore86 or Geode.

 

[3dcgi]

I don't know when or if an ISA expires, but x86 has been around for longer than 20 years and without the newest extensions like 64-bit and SSE/AVX it's not useful. It's possible the ISA isn't patented and has trademark or copyright protection instead which last longer.

 

[pcchen]

AFAIK you can't patent an ISA, but you can patent some implementation details essential for implementing an ISA. It may be possible to implement x86 without those patents, but it's likely to be inefficient.

As patents expires, companies normally file new "improvements" based on old patents, to extend their useful life. For example, the basic x86 ISA may rely on some old, expired patents, but you may need some new patents to implement MMX and SSE (and further extensions such as x86-64 and AVX). So, you may be able to make a vanilla x86 CPU using these expired patents, but no one is going to buy one.

Trademark problems are easier to solve, though. It's already established that numbers alone can't be trademarked (that's why Intel moved from '80486' to Pentium). So just call your CPU 'compatible to 80386' and it'd be fine.