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A fix for Vista only seeing one CPU in Boot Camp Install
I've been using Vista Ultimate on my MacBook Pro (Core 2 Duo), and since installing the latest Boot Camp drivers package, it only saw a single core. When booting up, prior to the GUI loading, it would show one system processor in the plain text area where it lists the Windows version. Once fully booted up, the Task Manager's performance window would only show one processor, although Device Manager did show two processors and the About window (right-click My Computer » Properties) did list the CPU as a dual core, though all performance measuring apps listed one as available.

To fix this, you will need to access the Vista NTFS partition from another OS. There are a few hints on how to do this (here's one), and I followed the installation of MacFUSE and NTFS-3G, unmounted the read-only Vista partition, created the directory /Volumes/Windows, then remounted it using the command line:
sudo ntfs-3g /dev/disk0s3 /Volumes/"Windows" \
-o ping_diskarb,volname="Windows"
Then I typed:
ls -al /Volumes/Windows/Windows/System32
You will see three files: hal.dll, halacpi.dll, and halmacpi.dll. You will likely see that hal.dll is the same size as halacpi.dll and halmacpi.dll is a different (larger) size. If this is not the case, then stop reading this hint as it does not apply to you.

If this is the case, rename hal.dll to hal.original by typing:
$ cd /Volumes/Windows/Windows/System32
$ mv hal.dll hal.original
Then make a copy of halmacpi.dll and name it hal.dll by typing:
cp halmacpi.dll hal.dll
What you've just done is taken the old hal.dll (which if I recall correctly stands for Hardware Abstraction Layer) for single core CPUS and replaced it with the multi-core version. Now, all you need to do is reboot into Windows, and you should see two system processors in the text list prior to GUI, and Task Manager should show two CPU fields. Your system will also be a lot faster.

[robg adds: I haven't tested this one, as I've not yet taken the plunge into Vista on my Boot Camp partition.]
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A fix for Vista only seeing one CPU in Boot Camp
Authored by: diamondsw on Sep 24, '07 09:16:22AM

Correct me if I'm wrong, but you can also do this within Windows. Go into the Windows Device Manager, and if "Computer" is set to "ACPI Uniprocessor PC", you can simply update that driver to the "ACPI Multiprocessor PC" and be done.

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A fix for Vista only seeing one CPU in Boot Camp
Authored by: shadowtech6209 on Sep 25, '07 12:09:36AM

Right. You can switch the number of supported CPU's on-the-fly, but you cannot choose whether to use ACPI or MPS or the more vanilla APM without first reinstaling the ENTIRE Windows OS.

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