Spontaneous partial cure for insomnia on ThinkPad 600X

This is a tale of Linux and a ThinkPad 600X that I installed Mandriva 2005 onto a while back. I hadn't been able to get it to sleep properly. And it was especially irritating because rather than failing in a normal way, what would happen when I closed the lid and then re-opened it later was that the screen would come on, display the screen that it had when it was closed, but THEN it would reboot from scratch.

I would have suspected that this might be insoluble, but I'd used liveCDs on this machine, and a few of those behaved a bit more gracefully, with caveats. Knoppix 3.6 or so would deal with a close of the top by not actually spinning down and sleeping, but turning the display off and on at the appropriate points. Knoppix 3.7 and later do the spinning down, sleeping and waking thing ALMOST correctly -- after the unit wakes up, most of the stuff works except for sound applications. Dynebolic liveCDs seem to behave similarly.

So I tried the various power options that Mandriva ships with, and I tried the ThinkPad Mandriva module, and I tried the stuff on the various (excellent!) Mandrake-Thinkpad 600X sites. No improvement in Mandriva's behavior, so I hypothesize that since the sites were all from 2002 or before, then it might be something newer that makes for the oddness. And from there, it's just a process of elimination involving taking careful notes and such.

But before I got around to this, I noticed some interesting bits in the release announcement for Kubuntu 5.10, which came out recently. I burned a liveCD of that and booted from it. Its sleeping capabilities seemed on a par with recent Knoppix releases.

And I was telling a friend about all this, and rebooted the 600X under Mandriva to show the odd sleep behavior. But no, it didn't do it's old trick, this time! Now it doesn't spin down, but it powers the display on and off just fine.

That's encouraged me to start hoping I can make this machine my default laptop, and I've even started checking out KDE-specific stuff like Knotes, with which I'm typing this as a test post.

So, I know the ThinkPad 600X is an old machine, but I'm wondering how it is that a LiveCD can change its sleep behavior in a way that lasts, or did something in Mandriva change itself when I wasn't looking?

--