How can I deliberately slow Windows?

Question

How do I reversably slow a PC with XP?

I want to achieve this without using visible CPU-cycles, so I'm guessing some hardware settings might do.

I don't want my app to run slow, I want the whole OS to be slow. I know some network lookups especially out of a trusted environment (think Active Directory) slow a PC way down. This is the effect I want.

Disclaimer: this is not for a bad/evil/illegal cause!

Answer 1

We use a 'crippled' server we call doofus for load testing. it is an old P3/500 box with limited RAM.

Another option is setting up a VM with very limited resources.

Answer 2

If you think your hardware setup can handle it, some motherboards let you manually specify a clockspeed multiplier or other speed settings in the BIOS. Often there'll be an option for a slower speed or a field where you can manually enter a lower multiplier.

If not, you might consider setting up a virtual machine, and making sure it's not fully virtualized - paravirtualized machines run slower due to the necessary translations that take place in the virtualization layer.

Answer 3

Remove the thermopaste and put some dust on the CPU :-) Also, remove some RAM.

Answer 4

Use powercfg.exe, to force the computer to a power plan you've created that locks the CPU into a lower frequency to conserve power. What states are available depend on your platform (most desktops only have a couple.)

Answer 5

We keep an old laptop around for this reason. Helped me to find a subtle timing issue in some splash screen code that was absolutely unreproducable on decent quad core dev boxes.

Answer 6

You may want to take a look at a full-system simulator such as Simics. Simics allows you deterministically simulate an entire system (including networks, if you want). Not only can you tweak the CPU frequency, you can study the system in detail to see how it behaves.

Unfortunately, Simics has quite a pricetag.

Answer 7

The open source Bochs emulator is pretty easy to slow down by editing its config file. Windows XP will run in it. It is not as powerful as vmware, but there are many more configuration options.

Look at the documentation for the config file, "bochsrc", and particularly the "IPS" entry. (Instructions Per Second)

Answer 8

If you want to see really dramatic effects very easily, set the /MAXMEM switch in boot.ini (or use msconfig). This will limit the amount of memory used by the system - switching to 256mb or lower would make things very, very slow.

Answer 9

Install Norton 360. It makes the mouse cursor lag during updates and constantly nags for restarts.

Answer 10

You have lots of options. Things I can think of:

1. Change your disks to good old fashioned IDE. None of that high-speed DMA stuff, just good old fashioned PIO.
2. Remove RAM (or diable in the BIOS)
3. Switch to generic video drivers (I mean "Generic SVGA" type, that are un-accelerated)
4. Disable core(s) in the BIOS
5. Slow the CPU down in the bios (if possible)

Answer 11

Disable the L2 cache in the BIOS

Answer 12

Two Windows applications: Mo'Slo and Cpukiller.

I remember hearing of one that grabs large chunks of RAM, to reduce your available RAM, but I forget what it is called.