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garfield
11-03-2001, 02:32 PM
Hello, there,

I have a general question about how OS interact with BIOS.

Mordern OSes run in protected mode, while most BIOS codes run in real mode. The result is the OS cannot call most BIOS functions directly. I'm aware that some BIOS calls are designed for protected mode.

Here's a more specific scenario. Once a PnP OS is started, it will detect new device plugged into the system (e.g. insert a network card into a laptop running Windows 95.)

Generally speaking, once the OS loader switches the CPU into protected mode, it needs a generic method to communicate with BIOS codes.

My questions are,

(1) Is there such a generic communication method (or industry standard API) like this?

(2) If protected OS may call protected BIOS code, how does BIOS know those GDT, LDT and IDT etc?

(3) In case of the above PnP scenrio, could anybody explain a little bit technical details?

(4) Where can I find BIOS techinical specifications?

Thanks in advance,
geebee76
11-03-2001, 06:17 PM
Hi Garfield, Welcome to the Forum.

This stuff is a little over my head but I did come across this (http://x86.ddj.com/articles/pmbasics/tspec_a1_doc.htm) whilst researching another post. It may be way off the mark but still worth a look.

http://www.PCGuide.com/ubb/smile.gif

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garfield
11-03-2001, 07:49 PM
Thank you so much, GeeBee. The link is very helpful.

I'm familiar with Intel CPU pretty well, but not other details like PIC, A20, BIOS, and interactions between them as described on this web site and the page you recommended.

Today, most programmers don't care about low level things like these. The OS takes care of it. It's becoming more and more difficult to learn technical details about it.

Originally posted by geebee76:
Hi Garfield, Welcome to the Forum.

This stuff is a little over my head but I did come across this (http://x86.ddj.com/articles/pmbasics/tspec_a1_doc.htm) whilst researching another post. It may be way off the mark but still worth a look.

http://www.PCGuide.com/ubb/smile.gif