Strange Laptop Freezing

[RRunner]

I wasn't sure where to post this... hope this is ok.

I am having a problem with an HP laptop that someone has asked me to take a look at. It is an ok machine for what they want to do with it (Celron 1.6 Ghz with 1 Gb ram). The HD was dead so I put in an old one that I had kicking around.

While trying to re-OS it I ran into a strange problem. The machine would freeze periodically. I noticed that there was a lot of flex in the chassis (a lot of missing screws) and when I moved it, the laptop would suddenly un-freeze and continue as if nothing had happened! Any type of physical contact with the laptop seems to cause it to freeze and a slight lift or twist of the chassis will un-freeze it as if nothing had happened. Weird.

Note that if I type on the keyboard while it is frozen, the letters I type show up after I give it a twist and it un-freezes! If I move the mouse when it is frozen, the cursor is moved instantly to the new location (relative to the mouse movement) after I give it a twist and it un-freezes. So very weird.

Before I rip this thing all apart looking for loose connections, etc... does anyone have any ideas where I should start looking? I find it really odd that there could be a loose connection or grounding problem that would freeze the machine (mouse doesn't even move) and given a slight twist, it resumes function without crashing!

[koshman]

It looks like an issue with display. The NB probably still works when you think it froze, only the video output doesn't update. Check the display cable?

[Tension]

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[odin]

Does the caps lock LED toggle when you hit caps lock when it is in frozen state?

[Lando]

Do you have any way of plugging it into an external display to see if, as already suggested, it is just the LCD not updating?

[tone007]

Sounds like some component on the board is loose, probably due to it being flexed. (Picking up a laptop by one corner is a bad idea, but people do it all the time.)  Could also just be something shorting, though.

[AmigaHeretic]

OH MY GOD!!    I had this exact same problem with an HP laptop.

To me it was one of the most amazing issues I've ever seen.   So amazing I made a youtube video of it!

http://www.youtube.com/watch?v=ixGIfBrW5wM


(Laptop shown running WinUAE then in Windows)

It's not a monitor issue.   When you twist the motherboard portion it "pauses" the entire computer system.


I tested it several ways.  First, I would twist it a little and get it to freeze, then I would leave it frozen for a few minutes and then twist it back to unfreeze it and the clock would stay several minutes behind.


I tried rendering, would twist to freeze the system, wait a several minutes, then unfreeze it and the render continued exactly where it left off.


Tried with downloads too.  Started to download a file that would take aprox. 30 seconds, would 'freeze' the system for about 5 minutes, then unfreeze and the download would continue right where it left off ( wish I had tested this part more)


At one point I had left it frozen for several hours, twisted it to unfreeze it and the clock was several hours behind.

Unfortunantly it was a relatives Laptop and I never got to disassemble it.  (They just bought a new one)  


I thought that it would be awesome to figure out how this AMAZING fault worked and create a "PAUSE" button for my desktop.

I was amazed that the everything could be paused for so long, have no memory corruption after several hours, and seem to pick up on the next CPU cycle it left off on.


Pretty crazy.  I never thought I'd see a similar issue again.

[RRunner]

@AmigaHeretic: That is EXACTLY what I am experiencing. If you put your hands on the laptop to use it, the thing freezes. In my case, if I lift up on the bottom left corner of the computer (left of the track pad) it will unfreeze. It is just as if you have put the computer into some form of suspended animation. Everything freezes as if time has stopped. I don't understand how that is possible without causing a crash but even the clock stops. So weird. I'm going to tear it apart when I get a chance and see if I can spot anything.

@Lando and koshman: It is definitely not just the screen display freezing. If I am doing something that involves reads / writes from the HD, the HD stops spinning when it freezes then the HD operation picks up right where it left off when it is unfrozen. At first I thought it was just a display problem but further tests quickly ruled that out.

@odin: Nothing happens when it is frozen. The cap lights key doesn't go on/off when frozen but... if it is frozen, and I click the caps key... then unfreeze it... the cap locks goes on/off immediately after it is unfrozen. Looks like the key stroke buffer still functions while it is suspended. Also, if I plug in the network cable, I can see activity (lights blinking) while frozen. The computer is not actively responding to requests while it is frozen though.

@tone007: I agree. I'm going to tear it all down when I get a chance.