[vbox-dev] Can't use more than one vCPU after upgradingtoVirtualBox 4.3.x

Frank Mehnert frank.mehnert at oracle.com
Mon Dec 30 17:06:21 GMT 2013

Hi Tal,

we use GetLogicalProcessorInformation() to determine the number of physical
cores, see here:


Kind regards,


On Saturday 28 December 2013 18:14:54 Tal Aloni wrote:
> Thanks Frank,
> I see 4 CPUs in the host Task Manager, which Windows API call do you
> suspect the issue lies with?
> Tal
> ----- Original Message -----
> From: "Frank Mehnert" <frank.mehnert at oracle.com>
> To: <vbox-dev at virtualbox.org>
> Sent: Saturday, December 28, 2013 6:51 PM
> Subject: Re: [vbox-dev] Can't use more than one vCPU after
> upgradingtoVirtualBox 4.3.x
> Hi Tal,
> as I thought: You have a newer AMD processor and Windows returns the
> wrong number of cores for your CPU: It returns 1 when your CPU has 4
> physical cores. We use a Windows system function to determine the number
> of physical cores. I think that's a Windows bug and we need to find
> a workaround. To be able to assign more guest CPUs to your VMs you
> can use 'VBoxManage modifyvm VM_NAME --cpus ...'.
> Kind regards,
> Frank

Dr.-Ing. Frank Mehnert | Software Development Director, VirtualBox
ORACLE Deutschland B.V. & Co. KG | Werkstr. 24 | 71384 Weinstadt, Germany

Hauptverwaltung: Riesstr. 25, D-80992 München
Registergericht: Amtsgericht München, HRA 95603
Geschäftsführer: Jürgen Kunz

Komplementärin: ORACLE Deutschland Verwaltung B.V.
Hertogswetering 163/167, 3543 AS Utrecht, Niederlande
Handelsregister der Handelskammer Midden-Niederlande, Nr. 30143697
Geschäftsführer: Alexander van der Ven, Astrid Kepper, Val Maher
-------------- next part --------------
A non-text attachment was scrubbed...
Name: signature.asc
Type: application/pgp-signature
Size: 198 bytes
Desc: This is a digitally signed message part.
URL: <http://www.virtualbox.org/pipermail/vbox-dev/attachments/20131230/3c821e37/attachment.sig>

More information about the vbox-dev mailing list