I wonder why the entire message board for Laptops General seems to be locked. That board has several discussions about M6500 blackouts but I cannot add to any of them, though in fact this board Precision Mobile Workstations is more appropriate for this particular issue.
Nvidia has a secret driver for the Quadro FX 3800M chip which appears to help solve the blackout problem!
Nvidia's driver search page is:
Quadro FX Series (Notebooks)
Quadro FX 3800M
Windows 10 64-bit
Optimal Driver for Enterprise (ODE)
Searching finds driver version 342.00 dated 2016-10-27:
Why doesn't searching find driver version 342.01 dated 2016-12-14:
Furthermore, the download page for version 342.01 is only available in English. 342.00 was available in multiple languages. (After downloading, it works OK in Japanese Windows 10 x64 and probably other language versions.)
Anyway, after installing 342.01, I also used the PowerMizer Manager tool. This time, instead of setting performance to medium as recommended, I set performance to minimum performance / maximum battery life, even when running on AC power. Furthermore in Computer Management - Services, I set both Nvidia Display Driver Service and Nvidia Performance Driver Service to Disabled. I think this combination of settings keeps the Nvidia chip consuming the least amount of power so it is least likely to overheat.
For a week now I have had no hangs, no blackouts, no problems even when awakening from sleep or hibernation.
A side effect of the new driver is that when awakening from sleep or hibernation, some windows get moved and resized, and some icons on the desktop get shifted around. I think the reason is that during sleep or hibernation the driver operates a simulated desktop instead of the real one, and the simulated desktop has size 1024x768.
For a Quadro FX 3800M and 1920x1200 screen, I think this can be fixed by the following set of registry changes. For a 2800M the key might need adjusting, and for a different screen resolution the numbers need adjusting.
Windows Registry Editor Version 5.00
The registry edits in my previous message do not help. When sleeping and awakening from sleep, Windows shrinks and moves some of my open application windows to fit in a 1024x768 portion of the screen, and Windows rearranges the icons on my dektop.
However, I haven't had a blackout or freeze or BSOD since installing driver 342.01 and using PowerMizer Manager to set performance to minimum.
In the HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\GraphicsDrivers\Configuration section of the registry, there are several subkeys, one or more subkeys representing the actual screen, a SIMULATED subkey which an older driver and/or older Windows version used when sleeping or closing the lid etc., and a few other subkeys among which one now is used when sleeping or closing the lid etc. and I don't know what the others are used for.
Adjust numbers in the 00 and 00\00 subkeys of ALL of those subkeys to match the actual screen size (and the stride which is 4 times the actual width, representing 4 bytes per pixel).
Now I can sleep without my windows getting jostled around.
And again, no hangs, no blackouts, no BSODs yet.
Nvidia's blackout defect affects Linux too, and someone experimented with disabling PowerMizer in Linux: