I recently bought a new MacBook Pro which sometimes goes too fast. I frequently program for Mathematica, and on my old 2007 MacBook Pro I usually got a feeling for inefficient code when it runs sluggishly (that's when I decide "gee, I wrote some garbage code. Maybe I should spend a couple hours fine-tuning it"). However, on my new Mac, everything just runs zippy fast.
Is there a switch on the Mac that lets me slow down the CPU to, say, 1 GHz?
I do not think it is possible to manipulate the minimum clock speed bar, simply because of the direct relation between power, frequency and the clock speed of a micro processor. Obviously the clock has a range, so for example for running simulations the system takes more power to run faster under the range, and then when you stop simulating you see the drop.
A Solution: Alternatively did you consider, running the programs within MAC OS but on an virtualizer (e.g., virtual box)? You can then limit the number of cores/RAM dedicating to running the second OS. In that case, the programs can forced to be run much slower; because the virtualizer has much lower resource. This will give you much more flexibility and in case of a failure, you can go back and change the virtualizer settings. More interestingly, you can bring the packaged settings that run on the virtualizer to another machine and run it there as well, by having the virtualizer there of course.
If your concern is how efficient your software is, let me suggest a more engineering-oriented solution that will let you keep your MacBook running at full speed:
Use the profiler built into Mathematica. This will let you identify the parts of your computations that consume the most time without having to resort to seat-of-the-pants measurements that only work on slow hardware.
Profiling, as suggested in Blrfl's answer, is the more appropriate way to identify whether or not your Mathematica code is efficient. However if you really want to slow down its execution, you may be able to do this by changing the priority of the Mathematica process. I haven't tried this but you may find helpful information or software among these links:
Is there any way to set the priority of a process in Mac OS X?
How to permanently “renice” a process on Mac OS X (or iOS, etc)?
Appriority (formerly Renicer) by Northern Softworks
Some of those discussions are a bit old though, so you may need to experiment or search further to find what works on your Mac and OS X version. Also you may find the technique works more effectively if you set your Mac some other heavy processing task to run at the same time - converting a big video file, say.
Unfortunately, no. You can't alter the clock speed on Macintosh computers. They don't have a BIOS in the same way that Windows motherboards do, so there's no way the user can change the clock speed or fiddle with I/O stuff.
The reason for this is mostly because on a Mac, you don't need to manually change these things. The hardware is already pre-built and the OS knows what hardware it will/can be attached to.
Yes, but it's not advised. The clock speed is controlled by the OS and the processor itself due to a number of factors, including processor load, temperature, and power availability.
If you reduce the battery to 10-20%, disconnect any external power source, and heat the laptop up to its maximum operating temperature, 95F (35C), it will certainly enter a lower power state, including reducing the processor clock significantly. A small heating pad, such as those used for back pain, below the laptop may be sufficient, and during the winter may be very comfortable for you.
However, it would be better to use the correct tools for performance tuning. Yes, you can simulate your old environment and thereby use your own internal clock, however the software you're using has clocks, timers, and other tools to understand the performance of your work. Given that you may likely upgrade again in several years, or you may use different computers and computing platforms in the intervening time, using crutches like emulators isn't a good long-term solution.
I suggest you instead make use of the built in tools. Regular use will allow you to use them without too much additional effort, so that you can integrate them into your software on the fly.
