Mr. Dee, MS is making 64-bit versions of Longhorn for Intel and AMD CPUs. 64-bit Longhorn Alphas were part of the bits given to PDC devs. The next .NET runtime will be available for 32 and 64-bit platforms, and in most cases, allow apps to take advantage of 64-bit CPUs without code modification.
RE: Seperate versions of Windows 64-bit
MS could distribute multiple versions of Windows (32 and 64-bit) on the same disc (might need a DVD) like they did with NT 4. I think one of the reasons there are seperate versions now is due to the timing of the different CPUs' release in relation to the OS' development schedule, and the different target markets involved. When Intel released Itanium, it was (and is) targeted at high-end servers and workstations, and required MS to make changes and optimizations to the OS that wouldn't be ready by Windows 2000's launch. Also, the 64-bit versions of Windows currently aren't as feature complete as their 32-bit counterparts mainly because those features weren't important to the target market.
With AMD64, 64-bit is mainstream, and will be moreso as newer CPUs are released and the price continues to drop. Before Longhorn, MS has AMD64 versions of Windows XP and Server 2003 coming soon (currently in Beta, RTM next year). Longhorn will likely have full feature parity between 32 and 64-bit versions, and the fact that the majority of Longhorn's codebase is managed will greatly help with this, as well as supporting and optimizing for other CPU architectures that come along. Unlike with NT 4, where apps had to be recompiled to run on each of the supported CPUs, Longhorn managed apps should run without modification on any CPU MS supports with the OS. There are likely some exceptions to this, such as managed apps that call unmanaged code, but for the majority of cases, this will be true. The next .NET version (pre-Longhorn) is Codename: Whidbey, which is what will initially provide this capability. Longhorn's version of .NET is Codename: Orcas.
RE: 32-bit apps on 64-bit OS
For unmanaged 32-bit x86 apps, Microsoft's Windows on Windows 64 (WoW64) layer allows these apps to run on different CPU architectures (much like how WoW32 allows 16-bit apps to run alongside 32-bit apps on Windows currently). Intel is supposed to be reworking Itanium to run 32-bit apps faster, however, WoW64 will allow you to run these apps on 64-bit CPUs by using native CPU compatability capabilities if available (like AMD64) or through emulation on architectures that don't execute 32-bit x86 natively.
This post was edited by n4cer on Thursday, November 06, 2003 at 16:56.
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