In an alternative universe without AMD64, Intel would have kept pushing Itanium while sorting out its issues, HP-UX was on it, and Windows XP as well.
People don't read comments before replying?
Or maybe, if the push came to shove, the desktops would switch to something entirely different like Alpha. Or ARM! Such event would likely force ARM to come up with their AArch64 several years sooner than it actually happened.
With how long it took Intel to ship expensive, incompatible, so-so performance ia64 chips - your theory needs an alternate universe where Intel has no competitors, ever, to take advantage of the obvious market opportunity.
4gb of RAM existed but many many systems weren’t even close to it yet.
Without AMD, there was no alternative in the PC world, It was already the first 64 bit version of Windows XP.
Since we're providing suggestions in computing history, I assume you can follow the dates,
https://en.wikipedia.org/wiki/Windows_XP_editions#Windows_XP...
Perhaps? I don't know enough to judge whether one of the other companies working on IA-32 compatible processors could plausibly have stepped in -
https://en.wikipedia.org/wiki/List_of_former_IA-32_compatibl...
It's true that most of those would have lacked the resources to replicate AMD's feat with AMD64. OTOH, AMD itself had to buy out NexGen to produce their K6. Without AMD and/or AMD64, there'd be plenty of larger players who might decide to fill the void.
Eventually Intel gives up after motherboard/desktop/laptop makers can't build a proper market for it. Maybe Intel then decides to go back and do something similar to what AMD did with x86_64. Maybe Intel just gives up on 64-bit and tries to convince people it's not necessary, but then starts losing market share to other companies with viable 64-bit ISAs, like IMB's POWER64 or Sun's SPARC64 or whatever.
Obviously we can't know, but I think my scenario is at least as likely as yours.
Considering that PAE was a gimmick anyway.