virtualbox.org

We use VirtualBox for simple things. We want give each virtual machine the least amount of resources, but enough where they still perform well. Of course our Hypervisor host is running Windows and it is 64bit. We do not do many demanding things on the virtual machines. Mainly a lot of demonstrations of common things you do with Windows OS. My question is, to get the best performance should we run 64bit or 32bit virtual machines? Thanks

First let's clear up some likely confusion: a 32bit application is one which is designed for a 32bit OS. It doesn't mean that the application is restricted to 32bit CPU operations, so if 64bit CPU ops can make it faster then being a 32bit native app is not an obstacle. I assume you're also aware that what "32bits" mainly implies is that the host OS has a max 4GB of total RAM for everything (if it uses a flat memory model), and generally can't offer more than 2GB to an application. The benefit of moving to 64bits is that the application can now allocate >2GB physical RAM in contiguous chunks - a benefit which of course is moot if the app has no use for that kind of memory - as most apps don't.

Generally speaking, a 32bit application will perform faster on the same hardware because it tends to move less data around, and memory bandwidth has been the real bottleneck in PCs for quite some time now, not CPU clocks. On the flip side, if your application is one of those few which requires access to huge amounts of memory then 32bits would cripple it.

Office applications gain nothing from 64bits, so they'll tend to be a tad slower, but probably not so you'd notice (the same apps get nothing from multiple cores btw, with the possible exception of a spreadsheet app running a horrifically complex spreadsheet). OTOH video rendering etc can probably find a use for all the cores you can give it.

If you do a lot of 3D CAD with huge models then it can be quite amazing how much memory that gobbles up. Those apps really benefit from >4GB RAM.

Thanks that help a lot!