VirtualBox - XP guest does not see multiple cores/multiple processors

Question

Environment:

• Host OS: Win7 Pro 64bit
• Guest OS: WinXP 32bit
• VirtualBox version: 4.1.4r74291
• Processor: Intel Core i7 2630QM with virtualization enabled

The Problem:

I need the guest system to use multiple cores. I have enabled the following options in VirtualBox:

• IO APIC (motherboard tab)
• PAE/NX (processor tab)
• VT-x/AMD-V (acceleration)
• nested paging (acceleration)

All other options on the System submenu are switched of. The 'processors' slider is set to 8.

The problem is that the guest system runs correctly, but only one processor/core is visible.

Answer 1

XP has 2 different HALs that are used for multi and single processor. If you installed XP when the virtual environment only had one processor then you may have to change the HAL or re-install.

You can find instructions on how to change the HAL on Microsoft's support site.

You'll need to select the ACPI multiprocessor option.

Answer 2

This worked for me (VirtualBox XP Pro)...

1) Go into c:\windows (your install path), search for sp3.cab. Open this cab file with 7-zip (although explorer may be able to natively open the file, if it can't then download 7-zip from sourceforge).

2) a) Extract halmacpi.dll to c:\windows\system32

b) Extract ntkrnlmp.exe to c:\windows\system32

3) Edit c:\boot.ini

Note: You will need to uncheck the Read-only property so you can save your changes. Set back to Read-only once complete.

Copy the line that looks like this:

multi(0)disk(0)rdisk(0)partition(1)\WINDOWS="Microsoft Windows XP Professional" /fastdetect /NoExecute=OptIn

Make the copied entry look like this:

multi(0)disk(0)rdisk(0)partition(1)\WINDOWS="Microsoft Windows XP MultiCore" /fastdetect /NoExecute=OptIn /kernel=ntkrnlmp.exe /hal=halmacpi.dll

Now you have a dual-boot option to utilize single or multicore (TaskManager will show two CPU graphs if this was successful). If multicore boots and works properly, then you can delete the single core entry from boot.ini.

Answer 3

Just looking for the solution [my winxp saw 1 core out of 4] and I stumbled on this: http://www.nforcershq.com/forum/updating-the-hal-for-multiprocessor-support-t70331.html

I downloaded the devcon util from MS and issues the command:

1. devcon sethwid @ROOT\ACPI_HAL\0000 := +acpiapic_mp !acpiapic_up
2. devcon update c:\windows\inf\hal.inf acpiapic_mp.

[I had an error on the 2nd command so I removed the . [dot] at the end]

Then rebooted and now winxp can see all the 4 cores.

Make a backup of the image before starting in case the system won't boot anymore!