Computing History & Emulation

An Intel Itanium Emulator That Finally Boots Windows

A new open-source emulator written in Go successfully boots the Itanium version of Windows Server 2003 and Windows XP 64-bit — bringing one of the most ambitious and unsuccessful CPU architectures back to life.

• Built by Yufeng Gao with help from gdwnldsKSC, the version-0.1 emulator runs the Itanium edition of Windows Server 2003 and Windows XP 64-bit Edition natively inside software.
• It runs roughly at the speed of a 1990s Intel 486 on a modern Ryzen processor — slow, but running, which is the whole point.
• Linux, BSD, HP-UX and OpenVMS do not yet boot, but this is the first known working emulation of the architecture.

The Intel Itanium (IA-64) is one of the great road-not-taken stories of computer engineering. Conceived by a partnership between Intel and HP, it was designed to leap past the compromises of the x86 line that had quietly evolved for decades. Instead of letting the hardware decode instructions on the fly, IA-64 used an approach called EPIC — Explicitly Parallel Instruction Computing — pushing the job of finding independent operations into the compiler, where it could be done once at build time rather than billions of times per second inside the CPU. It was a beautiful idea that the compiler industry simply was not ready to exploit.

After a rocky launch, Itanium was squeezed out by the simpler AMD64 extension, which gave 64-bit computing with near-total backward compatibility. By the late 2000s the chips were surviving only on HP servers running HP-UX and OpenVMS, and Intel eventually wound the line down. For anyone curious about how an IA-64 program actually executes, that meant there was nowhere to run one. Until now.

The emulator is being written as an open-source project (the Rosalia64 effort, in Go) and its first release already manages to get a full Windows desktop up on screen. Performance is nowhere near useful for real work, but emulation is about proving the architecture can be recreated instruction by instruction; every bootable OS is a milestone. If development continues, the same project may one day run the Unix systems Itanium was actually built for — giving engineers a sandbox to study one of computing's most instructive failures at their own pace.