I have a T21 with a T22 motherboard and original 800mz chip. It's been about two years since the rebuild, and now it is doing that "freezing at a well known point" thing, that point being after the Windows moving bar moves about 6 times during boot. It then sits there permanently. Pressing and holding power button shuts it off.
I have gotten around this by cooling the laptop. It seems to be getting pretty hot underneath, and this problem *did* start in the summer when ambient temps are 10 to 20 degrees above normal. I've started running mobile meter after finding out about it here, but it hasn't frozen since.
I stuck it in the freezer for a few minutes to chill the hell out of it, pulling it out pretty early in case any condensation might form. This was after the last time it froze up, and it's been ok.
I suspect...definitely heat. Try running a fan pointed at the fan exhaust port. This keeps my temps below 50 degrees. I believe the max operating temperature for these chips is 70 degrees, but that is based on a regular (not speedstep or mobile) pentium III stat I found on the web.
On this page, it shows ranges of 60 degrees! to 85 degrees, so please post any shutdown temps you are getting...
http://www.heatsink-guide.com/content.p ... temp.shtml
Or if anyone knows for sure the operating range of an 800 or 900mz chip, please post.
I ordered a 900mz CPU, at which point I plan to clean the fan and apply new thermal shmooey. I guess that is what makes it do this after a few years in operation -- dirty fan and aging thermal conductant.
Also, I found out my issue may also be static electricity building up on the motherboard or chips. Power becomes dodgy during peak summer times, so brownouts and other weird things contribute to electrical failure. I read this solution for a different laptop, and this + the cooling is making it liveable...
Remove power cord and battery. Press down the power button for one full minute to discharge. Plug in ONLY the power cord, leaving out battery. Boot the PC. Add battery after boot, or after shut down.