I work in a test facility where we have to test some pretty new software on some pretty old kit. The developers who write the software test it on vmware workstation before it gets to me. They all have fairly recent high spec PCs and so the vmware guests perform quite well.

I want to tune those guests to work like the lowest spec of hardware I have to test the software on. Something like a Pentium III 1 GHz (!) with 1 GB of RAM. The RAM is obviously not a problem, how can I get the "cpu" in the VMs to act like a 10 year old PC?!

I was thinking of running some CPU stress tools, prime number generators etc, but that seems like overkill. I would like to stick to vmware workstation if possible.


In ESXi, you can set Resource Allocation limits for each VM. You can limit the number of MHz that the VM has access to. You can also do the same for Memory. I'm not sure if the same functionality exists in VMware Workstation.

Generally speaking, though, a sure-fire way to kill performance (especially when you're using slow hard drives) is to generate a ton of disk IO. You could use iozone or iometer to create a bunch of read/write IO.

  • That's great, thanks. I'm not too familiar with the vmware server products, but as vsphere is free then perhaps we can give it a go. ANd thanks for the tip on iozone, good to know :) – simon Jun 9 '11 at 21:00

Also look at WAN simulators to make your network virtually s.... ick ;)

But in general, I would expect real time behaviour of a slowed down vm to be still substantially different from an actual old PC, so buying a pallet of PIII/PII laptops off the surplus market will still give you more realistic results by far.

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