I think there is a fundamental misunderstanding about DOS-like
operating systems versus a protected mode OS like Windows.

> Doesn't the Pentium CPU have a disable instruction itself??? How would the OS
> be able to do "atomic" functionality (eg: for resource allocation) else????
> How would an interrupt protect itself from being triggered over and over
> and corrupting megabytes of memory with pushing status to stack over and over?
?

> Don't tell me it hasn't.

Of course the CPU has an interrupt disable.  Of course the OS kernel
has to use it.

But if you are an APPLICATION running under Windows, you CANT USE IT.

In protected mode (Linux, Windows, QNX, etc.) The CPU "protects"
memory segments and restricts instructions which attempt to cause a
context switch, under a protection scheme controlled by the OS.  Bill
Gates decides what your application can do and when.  Or never.
(I'll spare you my rant about the flaws in the structure chosen by
MicroSoft.  If you don't like it either, go buy Linux, or QNX, or
something.)

If you attempt to execute one of these priviledged instructions, or
memory that the OS has not given to you, as an application, the CPU
turns you over to the authorities.  This is known as a "Processor
exception".  In Windows the exception handler can give the user a
"This Application has performed an illegal operation..." Window.
This is known as "Being blown off the machine."  :)

To get access to system hardware and especially interrupt function
under Windows, you have to be a Device Driver.

Writing a Win32 device driver (a VxD) is not impossible, but its
non-trivial. Debugging a Vxd is definitely non-trivial.  (Want to
trade your Tait programmer in for a $5000 Pentium emulator?  Me
neither.)

That's why I moved over to embedded programming- working under the
Windows structure takes all the fun out of hardware hacking.  Which
brings us back on topic!  PICs don't have a protected mode, hurrah!

------------
Barry King, KA1NLH
Engineering Manager
NRG Systems "Measuring the Wind's Energy"
Hinesburg, Vermont, USA
barry@nrgsystems.com
"The witty saying has been deleted due to limited EPROM space"