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First ever 64-bit version of Windows rediscovered … and a C compiler for it too

Nearly quarter of a century after it wasn't released, Windows 2000 for DEC Alpha found on a discarded disk

A 64-bit test build of Windows 2000 Professional for the DEC Alpha processor has been rediscovered – shortly after the discovery of a C compiler that could generate binaries for it.

Earlier this month, intrepid code archaeologists rediscovered a C compiler, based on DEC's C compiler for Alpha from the 1990s, that could generate 64-bit "Win64" binaries for 64-bit Windows on Alpha. Although this was an interesting find, it was just a curiosity, because there was no known 64-bit Alpha version of Windows out there in people's hands. Somebody somewhere had their memory jogged by this, and now that operating system has turned up.

This is interesting because it pushes the history of 64-bit Windows back a couple of years, and it's a product that, as The Reg reported way back in 1999, Microsoft denied would ever exist.

The build's existence has been known about for years, especially ever since celebrated Microsoft blogger Raymond "Old New Thing" Chen mentioned it in TechNet magazine in 2016. The fun part is that a copy has been discovered, shared online, and even installed and, via some inspired hackery, got running just this week.

The first desktop version of Windows to officially support 64-bit processors out of the box was Windows Vista in 2006. However, if you were really keen, it was possible to obtain Windows XP Professional X64 Edition – in fact, based on the Windows Server 2003 codebase rather than XP per se – sometime earlier.

These, though, were aimed at 64-bit x86 computers. Before AMD's Sledgehammer range of processors, announced in 2000 and on sale in 2003, the only official 64-bit Windows were server versions for Intel's ill-fated Itanium processor family, which The Register was already referring to as Itanic back in 1999. A preview 64-bit version of Windows 2000 Server for Itanium was released to Technet subscribers in 2001. All the other non-Intel versions of Windows 2000 were discontinued before the product was released, although 32-bit beta versions running on Alpha, MIPS, and PowerPC had been spotted in the wild. At launch, Windows 2000 was x86-32 only.

The new discovery reveals that there was already a 64-bit version of Windows – and a desktop edition, at that – over a year before even preview builds were officially, publicly released, which means that there's a target for the newly uncovered compiler.

No, this isn't of any particular use to anyone in 2023, but it's interesting all the same. Given that the Alpha CPU shipped way back in 1992, and NT shipped with a 32-bit Alpha version the following year, it's of note that it took so long – approaching a decade – for Win64 to become available even in test versions.

If this has made you wonder whatever became of Alpha, one eventual fallout of the 1998 Compaq/DEC acquisition, followed by the 2001 HP/Compaq acquisition, is that Intel ended up owning Alpha.

Obviously, the first pure 64-bit RISC chip couldn't be allowed to compete with either x86 or Itanium. Nothing else could, which perhaps explains why Intel flogged its Arm line to Marvell in 2006. ®


All right, yes, we know: if you're going to be pedantic, Windows 11 and everything before it are Windows NT under the hood. "Windows 2000" was just the branding that the Microsoft marketing department came up with. If you type ver at the command prompt, Windows 2000 identifies itself as Version 5.0. The Reg FOSS desk cynically suspects that the Windows 2000 moniker was intentionally chosen for its similarity to the unloved DOS-based Windows Millennium Edition so that customers would confuse them and buy the product aimed at lower-end systems.

And yes, we also know that Windows NT supported the Alpha chip from the very first version, NT 3.1, way back in 1993. However, all releases of Windows NT, from NT 3.1 to Windows 2000 at release, were 32-bit, so the Alpha version of NT was never able to use the 64-bit Alpha chip to its full potential.

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