[feature-request] Allow VM to run faster or slower than normal time

[Technologov]

bochs and DOSbox can speed up or slow down VM by emulating CPU and/or timer slower or faster than normal. I would like to have a similar feature here.

In virtualization world, a possible way to achieve this, is to increase/decrease timer interrupt injections, so VM can either run at 50% speed or 200% speed.

In this case clock time sync in Guest Additions must be turned off.

It is (sometimes) useful for gaming.

-Technologov

[Technologov]

having per-VM GUI slider for this feature would make VirtualBox unique among virtualization products.

-Technologov, 16.12.2009.

[Klaus Espenlaub]

This feature is already partially there, however not in the normal GUI or elsewhere. It has lots of rough edges, so we intentionally don't document it.

Just doing something because it's unique isn't necessarily a good thing. There are very few real use cases. Since every PC has a bunch of time sources, it immediately raises the question which one(s) should be affected. Would just add clutter without providing a real benefit for the vast majority of users.

[Technologov]

Great to know that foundation exists !

Well, as I said, it is useful for gamers. It adds very different gaming experience.

Some strategic games are too slow, and need some acceleration of the play process, and on the other side of the scale some shooters are too fast, and need to be slowed down.

As for different time sources -- best if all are affected.

-Technologov

[phil]

I just noticed this request and wanted to add support for it with another possible use case for this feature. I use Virtualbox to test our web sites and web applications on different browsers and operating systems. In general, I much prefer to be able to do this with Virtualbox on one machine, as opposed to having to start up several older machines to test older versions of Internet Explorer, for example. However, one thing that I can't currently replicate when I'm running Virtualbox on my fast development machine is the ability to test how fast or well Javascript runs on older, slower computers, or how quickly these older computers can render complex page layouts. Thus, I have often wished that Virtualbox had the ability to "slow down" the virtual machines in order to emulate older, slower computers.

I love Virtualbox and appreciate all of the efforts that the developers put into it, so thank you for all of your hard work.

[Technologov]

Your request is about slowing down CPU, while my request is about timer. Those are different features, and should be kept in different tickets.

Slowing down timer wont make CPU render webpages any slower. But yes, slowing down CPU may also be a valid feature request.

-Technologov

[Frank Mehnert]

Btw, this is VBoxManage setextradata VM_NAME "VBoxInternal/TM/WarpDrivePercentage" 200 for double speed of the guest clock. GUI support currently not planned.