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I am almost done coding my webapp-game. It runs on all modern browsers. However, I want to establish some minimum requirements for it.

Thus, I need a slow Mac. However, I don't have access to a slow Mac that has a modern browser (IE 9+, Safari 5+, Opera 11+, Chrome, Firefox 4+).

Using the tool mentioned in this question, I can simulate a slow Internet connection. I can use up plenty of memory easily. However, I have no clue how to simulate a slow CPU without resorting to underclocking.

Is there any way I can make my Mac's CPU slower temporarily without underclocking?

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also see Can i manually limit the cpu used by a process – gentmatt Mar 28 '12 at 6:02
cough Install Windows? :P – Russell Mar 28 '12 at 7:03
up vote 7 down vote accepted

One solution is to use virtualization to have another instance of Mac OS X running on your computer. Many virtualization applications (such as Parallels Desktop) let you decide how much resources an instance can have (e.g. memory or cpu). Lion increased its support of virtualizing Mac OS X.

If you do decide to go with Parallels, there's a useful how to article describing how to set up an instance of another Mac OS X Lion.

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Beat me by 20 seconds :) – penguinrob Mar 28 '12 at 3:11
Seems like this is both the community's favorite and my favorite answer. Green check for you! – JavaAndCSharp Mar 28 '12 at 10:28
In Parallels it seems like you can only limit the number of CPU cores but not the clock speed.. – Timo Jun 8 at 0:07
Seems like you can throttle the CPU using CPUThrottle – Timo Jun 8 at 0:13

You could always install OS X in a virtual machine and set the virtual machine to have a slower processor, perhaps.

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Run a few instances of yes > /dev/null &. Each instance will peg a core to 100%, so run one for each core. You could also try re-niceing the yes processes to a higher priority or lowering the priority the browser.

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Add sleep cycles to the main loop or parts of the code that runs often is a good first step. Next, add some calculations that are slow / irrelevant. Depending on what you want to stress, you can also so some awkward pointer math or casting of variables to slow things down. This is an easy thing to sandbag when programming.

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Thinking like a programmer. This is useful; however, I want to find the minimum clock speed at which the unmodified game can run. – JavaAndCSharp Mar 28 '12 at 3:21
Even when you are an Apple developer and take code to their testing labs where you can run it on all manner of hardware - do build in a nice margin of error since many user machines perform far worse than a best case mac. Between system add-ons and modifications, ram issues, full hard drives, etc... – bmike Mar 28 '12 at 3:24

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