I am starting to write a 64-bit kernel (x86_64, AMD64, wtv they're calling it now) and I am having trouble finding information involving long mode and the BIOS/APIC.
The APIC question is very simple: do all 64-bit processors have an LAPIC and I/O APIC? I kind of got that impression from Intel's documentation, but I would like to be sure.
In regard to the BIOS, is BIOS32 implemented on most/all x86_64 systems, or is it not something I can rely on? And can BIOS32 be used from compatibility mode?
I'm sorry if these questions are n00bish. Thanks in advance.
Long Mode, The BIOS, and APICs
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JohnnyTheDon
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Combuster
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Re: Long Mode, The BIOS, and APICs
No guarantuees either.
However both intel and AMD have introduced local APICs on-chip well before the 64-bit era started, and since its needed for multiprocessor support, it won't be going anywhere shortly. What other manufacturers do or might do, I have no idea. VIA has a 64-bit processor of which I know close to nothing.
The IO APIC however is located on the motherboard, which means that some chipsets might not support it (and I recall having heard something about motherboards not supporting dualcores, which might be related to that).
Paranoia therefore dictates that you should be able to anticipate on the absence of either or both.
As for the BIOS32, The same will probably hold - you should still not assume that it will be there.
However both intel and AMD have introduced local APICs on-chip well before the 64-bit era started, and since its needed for multiprocessor support, it won't be going anywhere shortly. What other manufacturers do or might do, I have no idea. VIA has a 64-bit processor of which I know close to nothing.
The IO APIC however is located on the motherboard, which means that some chipsets might not support it (and I recall having heard something about motherboards not supporting dualcores, which might be related to that).
Paranoia therefore dictates that you should be able to anticipate on the absence of either or both.
As for the BIOS32, The same will probably hold - you should still not assume that it will be there.
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JohnnyTheDon
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Re: Long Mode, The BIOS, and APICs
I was afraid of that. I guess I'll just have to rely on switching to real mode for PnP and changing the video mode 
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Thank you for the timely response.
.Thank you for the timely response.