Can't select more than 1 CPU

[dsplayer]

Did you look in your bios, and do you see anything about hardware virtualization?

This was the issue here. I had to enable "Intel Virutalization Technology" somewhere at the advanced tab.

[Bearvarine]

I was having this problem too on version 4.3.20. But after messing with it, I realized you cannot change the CPU count unless the system is stopped. After stopping the system, I was able to change it by moving the slider from 1 to 2 or 4.

It would be nice if there was some text on this page warning the user that the controls are disabled because the system is running.

[mpack]

It would be nice if there was some text on this page warning the user that the controls are disabled because the system is running.

Since that's what the greyed out text is already telling you, I don't see much point in making it more verbose.

It's an unfortunate truth that most PCs don't let you change the number of CPUs without powering it down.

[Pat99]

I know this sounds silly, but have you enabled BIOS settings? (virtualization technology enable)

[loukingjr]

I know this sounds silly, but have you enabled BIOS settings? (virtualization technology enable)

Did you read the posts?

[noteirak]

Everything in this thread relates to miss or lack of configuration from the user. I believe all the reasons also have been pointed out. I'll now lock this topic so people stop bringing it up from the dead.
Feel free to unlock if you feel it could still use some more love.