8 Nov
2007
8 Nov
'07
5:28 a.m.
Not sure about Windows95, but I guess at best it was
probably a
nasty mixed bag.
Windows 95 was capable of preemptive multitasking in theory. In practice,
the USER/GDI subsystem was still 16-bit and access to it was serialized and
shared between both 16-bit and 32-bit tasks, meaning a single 16-bit task
would effectively degrade the system to cooperative multitasking as the
16-bit task could not be forced to yield control in these critical sections.
The WoW Win16 system used in NT and modern Windows finally solved this
problem.
Even NT4,
which is purportedly preemptive has a few two many situations where/when
it can not be preempted. For example, when opening a telnet session, it
often can NOT be preempted until it gets to the point of success or failure.
The last time I had to touch NT4 is almost a year ago, but I do not
remember the system grinding to a stop when opening a telnet connection.