Tech Q: What is a

[Guest Dominik Mann]

Some days ago I read a post where somebody described Win 2000 and XP as "protected" operating systems. Can anybody explain to me what exactly this means?Thanks!

[Francois_Dumas 10]

I do not know the post but he might have meant that you need 'administrator rights' on those systems in order to be able to do all tasks on them (such as installing software). :-outta Francois :-wave________________________Francois A. "Navman" DumasAssociate Editor &Forums AdministratorAVSIM Online!email: fdumas@avsim.com________________________

[Vulcan 14]

It may also refer to the way the OS operates internal Francois.My limited understanding is that the OS is sort of 'ring fenced' to stop any application interfering with it and causing it to crash, like most OS's by 'the beast of Redmond' :-)I'm sure both of us will be put right when the original poster responds :-lol

[Guest Dominik Mann]

"I'm sure both of us will be put right when the original poster responds"That would be me :-) . Sorry, guys, I don't have any better information than what you theorized...

[Guest]

Hi Dominick,All of the NT based OS's from Microsoft (NT, 2000 and XP) run their low level OS code in Protected Mode (otherwise referred to as Ring 0). All Linux and Unix OS's (as well as many others such as BeOS) also run their cores in Protected Mode. All Win9x variants, on the other had, run most of their code in Protected Mode but some in Real Mode since a lot of the code is still 16-bit. Only 32-bit code can run in Ring 0 on an IA32 processor (all Intel and AMD processors since the Intel 386 - including the latest P4's and Athlon XP's).All IA32 processors have three "rings" of protected code, register and memory space:Ring 0 - OS Kernel runs hereRing 1 - OS system services such as device drivers, etc.Ring 2 - OS system services such as device drivers, etc.Ring 3 - All user applications, etc.What this comes down to is: The main 32bit XP Kernel can never be brought down by any device drivers or user application code that has frozen or otherwise errored because the Kernel of XP is run in the highest and fully protected Ring 0 where no other code has access.A misunderstanding of this is that XP cannot be frozen or Blue Screened unlike 9x... That is not correct. If a device driver necessary to display something on your monitor for instance (such as your video card driver) locks up, you of course cannot use your system anymore. Or if your mouse driver encounters an endless loop or the like, XP may blue screen. These are just a few examples.What is impossible on XP, however, is nothing can directly interfere with the Kernel's work and responsiveness. Unless the Kernel itself contains a bug, it will always be responsive to system calls on your machine. In a 9x system (or WinMe which is still a 9x system), some device drivers and indeed even some poorly written user applications can overwrite the memory space of the 16bit parts of the 9x Kernel that does not run in Ring 0 - immediately bringing your system to a halt. On XP, this is handled gracefully if possible and the offending application (which is run in Ring 3) will simply be shut down by the OS itself as it continues on. Applications can (and unfortunately do at times) mess with each other and cascade upon many other applications since they all run in Ring 3, but the OS itself and any behaved device drivers would still continue to be responsive (you still being able to hit CTRL-ALT-DEL is an example of this).There's a heck of a lot more to this subject of course, but thats the skinny of it. In the end, any true 32bit Protected Mode OS is inherently much more stable than a quasi 32-16bit or 16bit only OS. IA64 (Intel Itanium) and x86-64 (AMD Hammer/Opteron) platforms have even more protections built in, but are very similar in an end-user point of view to the existing IA32 processors. XP or Linux on those platforms will also run in Protected Mode.Sorry for the geek-speak, but hope that helps.Take care,http://members.rogers.com/eelvish/elrondlogo.gifhttp://members.rogers.com/eelvish/flyurl.gif

[Guest Dominik Mann]

Interesting, Elrond - thanks! :D Speaking of kernels and those nice things, I once got a bluescreen telling me about an "unexpected_kernel_mode", followed by a bunch of hexadecimal code and a reboot. Is that one of those occasions where even Win 2K and XP cannot "tame" a programme running wild any longer?

[Guest]

Exactly. Either a bug was encountered in Microsoft's Kernel code itself (rare, but happens), or a device driver errored and the system depended upon that driver to continue on (much more likely). The blue screen you get means XP was still responsive to this, but couldn't continue its work without the functionality that locked. In the future, I hope MS provides a lot more friendly information than they do now though, as those blue screens are pert-near useless to anyone outside Microsoft itself and thus are horrible starts to tracking the offending driver, etc down.Thankfully, this is becoming much more rare these days with true 32bit drivers that are at least somewhat battle tested (ie: signed by MS) and the Kernel itself coming of age after almost 15 years in existence. Linux and Unix systems are even harder to bring down like this since its code is open and available to all - this allows a heck of a lot more eyes to spot and correct potential bugs in a much shorter time.Take care, http://members.rogers.com/eelvish/elrondlogo.gifhttp://members.rogers.com/eelvish/flyurl.gif

[Vulcan 14]

Elrond,Thanks for enlightening me, and others; it is a long time since I read about the 'nuts & bolts' of the OS and about a similar amount of time since I had to deal with them on a daily basis, unfortunately.Take care, and watch that back ;-)

[Francois_Dumas 10]

You're the man, Elron ! :-) :-outta Francois :-wave________________________Francois A. "Navman" DumasAssociate Editor &Forums AdministratorAVSIM Online!email: fdumas@avsim.com________________________

[Guest]

Well, I don't know about that Francois... Sometimes I'm definitely the newbie (or the Troll :-lol), but in this case I'll simply say, "Thank You".:-)http://members.rogers.com/eelvish/elrondlogo.gifhttp://members.rogers.com/eelvish/flyurl.gif

[Guest]

Thanks for the back comment... I will and appreciate the sentiment.Best to you and yours, http://members.rogers.com/eelvish/elrondlogo.gifhttp://members.rogers.com/eelvish/flyurl.gif

[Guest]

Elrond: A most eloquent explanation; clear and simple, speaking to a complicated and confusing topic. I hope you don't mind that I ref. this thread in the Hardware Forum.Thanks,bt