It was a little over a year ago that I got Windows Vista up and running on my first-generation MacBook Pro by means of Apple’s Boot Camp, only to discover that it ran hot—so hot that it seemed pretty worthless. I believe that post (Vista on My MacBook Pro Is Hot—Boiling Hot!) has brought this blog more visitors than any other, which I count as solid evidence that many other Mac users have encountered the same problem and have gone searching on Google for a solution.
Unfortunately, all I could offer my fellow sufferers was the knowledge that they were not alone, but now I have a solution for them, based on the same “undervolting” technique I finally discovered to solve the even greater overheating problem I had encountered running under Mac OS 10.5.6, where temperatures would climb over 115° C and cause the computer to shut down unless I exited certain programs (rendered useless) or web sites in time.
I recently wrote What a Relief! MacBook Pro Overheating Problem Cured—Really, in which I told of finding a program called CoolBook to be the answer to my overheating problems. The basic idea behind the solution is that the computer’s factory-default voltages, which essentially determine the operating temperature, are for the different cpu clock frequencies substantially higher than they need to be. CoolBook enables one to reset these voltages to lower values, thus gaining much cooler operating temperatures, most importantly for the highest frequency, where sustained heavy-duty computing can lead to overheating. Undervolting with the help of CoolBook really gave me back the full use of my MacBook Pro. I refer anyone having similar problems to that recent post. The procedure for finding the lower voltages your particular computer can live with involves a fairly lengthy trial and error period, but it only needs to be done once.
I mainly wanted Vista on my Mac in order to test the Vista-compatibility of the Windows versions of my science education programs, OnScreen Particle Physics and OnScreen DNA. Having done that, and not having a new version to test, I could easily live without Vista; and the overheating problems encountered under 10.5.6 were much more serious for me. Nonetheless, it was an ongoing irritation in the back of my mind that Apple’s promise of being able to run Windows with Boot Camp was really a false one so long as the temperature went up so high under normal use. Thus it was natural to ask if I could apply the same undervolting procedure under Vista to eliminate the heating problem there as well.
Of course, CoolBook was no help for running Vista, since it is a Mac program, but a Google search for undervolting led me to a Windows solution. If you Google with the search string “undervolting guide,” you will find The Undervolting Guide, which tells you everything you need to know to undervolt under Windows. There is a free downloadable program called RMclock that allows you to reset the default voltages, just as CoolBook does for the Mac. The guide is written under the assumption that you have no previous information about temperature or the lower voltage limits at which your computer can operate stably. It leads you through a procedure similar to what I outlined in my post on Mac undervolting. Since I had already gone through this under Mac OS X and couldn’t see any reason why the lower-limit voltages would depend on the operating system, I assumed my results would still hold under Vista. The whole procedure seems a lot easier on the Mac side, so I would recommend anyone trying to cool down Vista on a Mac to determine lower-limit voltages under the Mac OS. Be sure to write down the lower-limit voltages you have found before booting into Windows to set voltages there.
I went directly to the RMclock instructions in the guide, skipping the parts dealing with stressing the computer at different voltages. You need to follow the RMclock instructions closely, as the procedure is considerably more complicated than what it is for CoolBook, there being several steps to go through before you reach the point of actually setting voltages. Things look quite a bit different too. Instead of showing the frequencies in physical units of MHz, RMclock shows “multipliers,” which are presumably the factors by which some reference frequency (unspecified) is multiplied to obtain the actual frequency. I just made the reasonable assumption that the maximum multiplier corresponded to the maximum frequency (2.004 GHz in my case) and set the voltage to what I had previously determined was sufficient under Mac OS X for my MacBook Pro. For the other multipliers I scaled accordingly, but chose voltages on the conservative side, i.e, a little higher, just to be safe. For keeping the maximum temperature down, it’s really only the top frequency voltage setting that matters much anyway. Lowering the other voltages below that used for the highest frequency just gives you a lower average temperature and longer battery life.
Did it work? Yes, I can run the most complex simulations of OnScreen DNA at a “cool” 80° C, instead of the previous 100° C. Undervolting has made it comfortable for me to run Vista on my MacBook Pro, so I don’t feel cheated anymore. Maybe I’ll actually use Vista for something other than testing my software now.