My amazing world

Tuesday, May 02, 2006

know about MS Windows OS

DO you know about this?

Will Windows work continuously for more than 49.7 days?

Here is a bit of information, which may surprise you all. Windows crashes
automatically if you don't switch off the machine for 49.7 Days. Microsoft
accepts this. Do you know why?

In Windows the Virtual Machine Manager (here after referred as VMM) is
responsible for creation, execution, monitoring and termination of virtual
machines. This VMM, which is a 32 bit, protected mode operating system
entity, provides a number of system services at chip level. One of these
services is "Get_System_Time". This particular service loads the EAX
register with the time in milliseconds since Windows started on that
machine. This service is accurate to 1 ms. EAX is a 32 bit register in Intel
386 Processor onwards.

So the maximum number of milliseconds it can hold is
(232)-1 = 4294967295 milliseconds = 4294967.295 seconds = 71582.79 minutes =
1193 hours = 49.7 days.
So after 49.7 days the EAX resets to zero. Most of the Drivers use this Time
Service to keep track of the Timeout of various services they provide. So
after 49.7 days the drivers cannot use the Get_System_Time function of VMM
and they crash taking the OS along with.


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