Macbook Pro imposibility to sleep by itself, is an OS X issue..not hardware

Question

I´ve already read evrey post about the issue of MacBook Pro´s not going to sleep by themselves. Mine got the same issue, I can make it go to sleep if I close the lid or using the Apple menu option, but by itself, the computer won´t sleep.
I know.... I´ve checked the Energy Saver Preferences, I´ve resseted the pre Ram, the PMU, deleted some preferences involving power management, preferences and.... nothing.
I created a new user, to check if there was any corrupted preferences in the user, and nothing, still my MBP won´t go to sleep by itself.
I even install Leopard in an extertnal firewire hd, to check if it had to do with 10.4.... and the same result. After that I erase this HD and installed 10.4.8, to see if it had to do with the latest updates ferom tiger...and the same...
At this point, and I´ve heard this in this forums, you´ll probably think it has to do with the hardware... But I´ve tried a third OS before sending my MBP to reapir... so I check what happens under XP using BootCamp...and Surprise! under XP my MBP manage to sleep by itself, as it should...
So by doing the maths, I guess there´s a problem with OS X, not with the hardware...
I´m not a programmer or anything like that, but I hope this experience help someone in this forum (or someone in Apple!!!) to find a solution to this issue and share it with us...who bought an extremely expensive machine that can´t sleep by itself!

Answer 1

sorry. I was feeling too lazy to type in a full explanation. Well this might still not be a full explanation to newbies but I'm going to try my best.
In Tiger or other classic operating systems, Apple used to set up each and every macs in such a way that when user puts them into sleep, the RAM will stay powered on. It will not turn itself off, which is why the computer won't have to write RAM's content onto your HDD and waste some valuable 3-4 GBs of space. However, failing to write RAM's content onto HDD will cause Macs to enable SafeSleep. So, therefore, in classic OSs, either SafeSleep was entirely disabled or not even integrated into old macs.
So, when the RAM stays powered on, doesn't sleep, computer doesn't and can't write data onto HDD, disk space doesn't get wasted and SafeSleep is disabled or doesn't exist, it's called hibernate mode 0. Since the computer doesn't have to turn off RAM, write its content on the Disk and turn on safe sleep, it can drastically reduce the amount of time it takes to both go into sleep mode and wake up from it. In my case, it takes no more than 6 seconds in total on average to sleep and wake up. Before, it used to take 12 seconds and computer too often failed to properly wake up from sleep causing me to go frustrated and reboot forcefully, which was bad for the computer, as pros claim.
However, it has a drawback. If your computer is sleeping, and you disconnect it from the external power source and remove the battery and swap it with another, you will lose all the data you have been working on. For example, if you were working in Adobe Flash and then decided to put the computer to sleep before saving your work and your computer is set to hibernate mode 0, if you swap the battery when the computer isn't plugged into an external power source, you will lose the unsaved work. It doesn't mean that all your data will be lost. The computer just won't be able to get you back to what you were working on. That's all.
With safesleep enabled, RAM is powered on while sleeping, but RAM contents are also written to disk before sleeping. In the event of total power loss, the system enters hibernation mode automatically. this has been introduced to machines produced on and after fall 2005.
Always remember that if you change to sleep mode 0 on a MBP, you lose the ability to do a battery swap without plugging the machine in. I wonder if doing so is really necessary and honestly speaking, i have never been in a situation where I had to do a battery swap at all, let alone doing it without plugging the computer into a power source. i'm carrying the magsafe adapter with me all the time in case my battery goes low and I have to make use of electricity.
And here's the final warning: you must disconnect all your bluetooth devices and turn off Airport before putting the mac book pro to sleep. I'm exaggerating a little but this would give you 95 percent guarantee that macbook pro would perform an uneventful awakening from sleep.
Try it and report back. And use the last sudo command to get back 3-4 GBs of space that were previously taken up by mode 3.