[vbox-dev] Monitor count limitations

Klaus Espenlaub klaus.espenlaub at oracle.com
Wed Jun 18 10:13:43 UTC 2014

Hi Rūdolfs,

On 18.06.2014 11:48, Rūdolfs Bundulis wrote:
> Hi,
> I'm developing a system that needs to run a headless VM with a large
> number of attached monitors - currently the GUI has the limit to set
> maximum monitor count to 8, I didn't check the COM API myself but I
> suspect that it will not allow me to set the count greater than 8, while
> browsing the VirtualBox sources show that the internal C macro is
> defined to 64:
> /* this should be in sync with monitorCount <xsd:maxInclusive
> value="8"/> in src/VBox/Main/xml/VirtualBox-settings-common.xsd */

Looks to me that this comment is simply outdated. Nothing more, nothing 

Many limits can be listed with "VBoxManage list systemproperties", and 
it shows 64.

> Is there really a need to limit the count to 8? If I change the xml
> schema file and increase the count from 8 to 64 and recompile would
> there be any actual limitations in the VirtualBox core?

There is a constant conflict in the GUI between sanity (i.e. protecting 
users against their stupidity - you can't believe how many people 
believe that more is better, even if it's a giant waste of resources 
instead) and allowing expert users to go to the extreme. There are 
extremely few people out there who ever need to deal with more than 8 

In my quick test I could use the GUI to select 20 monitors - sure, the 
slider doesn't allow that, but one can enter the number or use the 
up/down arrows. This needs 256MB of VRAM, which this high number 
automatically unlocks.


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