Re: Why code for 8295a still work on APIC platform?

Once I wanted to, but I  saw a similar question on the forum with no 
answer so I drop the idea. But now I decide to have a try. Thanks.

On 12/17/2014 01:59 AM, Stanislav wrote:
> Hello,
>
> Did you try to ask the question in the osdev forum ?
> I believe the osdev forum audience is more knowledgeable in such kind of
> questions.
>
> Thanks,
> Stanislav
>
> -----Original Message-----
> From: angwer [mailto:[email protected]]
> Sent: Tuesday, December 16, 2014 5:55 PM
> To: [email protected]
> Subject: [Bochs-developers] Why code for 8295a still work on APIC platform?
>
> Hi everyone, I am new here.
>
> Recently I use bochs as the emulator to learn OS development. I get some
> assembly code from a book, which manipulate interrupts. It initialize the
> 8295a PIC and IDT. I compile the code and then run it in freedos (since I
> have not written a complete boot loader, the book tells me to run it as com
> file in freedos, which makes no difference) and all goes well. The PIC is
> initialized correctly by sending ICWx and the handler is called when
> interrupt occurs.
>
> But I don't understand why the code can run correctly. I run freedos and the
> sample on bochs with the a  Pentium 4 cpu which uses xAPIC (I also test on
> core 2). I have search a lot and find that xAPIC is different from PIC and
> no results tell me they are compatible. (Actully when I read the Intel
> manual. I find 8295a can work together with APIC but it seems I can not use
> the usual way to initialize it.) So I think the code should not work. I
> don't see any code disabling APIC in the sample.
>
> So my question are:
> Why code using 8295a still work on APIC platforms?
> Does that mean cpus like Pentium 4 and core 2 still have PICs? And what
> about newer cpus?
>
> Sorry if the question is stupid and thanks everyone in advance.
>
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