[Qemu-devel] Intel 440bx hardware emulation correctness

[Qemu-devel] Intel 440bx hardware emulation correctness

[Cristi Magherusan]

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Hello,


Does qemu aim to completely emulate the Intel 440bx northbridge hardware
(and maybe other) to detail, or instead does it on purpose skip some
parts for the sake of simplicity?

As an example, I've seen that the RAM parameters are written in CMOS
instead of doing it using SPD and some RAM control registers, as
documented in the 440 datasheet. 

This only affects the BIOS code that does RAM detection, so the Bochs
BIOS code would also need to be changed accordingly.

Thanks,
Cristi

-- 
Ing. Cristi Măgherușan, System/Network Engineer
Technical University of Cluj-Napoca, Romania
http://cc.utcluj.ro  +40264 401247

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Re: [Qemu-devel] Intel 440bx hardware emulation correctness

[Cristi Magherusan]

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On Sun, 2009-07-26 at 14:35 +0300, Cristi Magherusan wrote:
> Hello,
> 
> 
> Does qemu aim to completely emulate the Intel 440bx northbridge hardware
> (and maybe other) to detail, or instead does it on purpose skip some
> parts for the sake of simplicity?
> 
> As an example, I've seen that the RAM parameters are written in CMOS
> instead of doing it using SPD and some RAM control registers, as
> documented in the 440 datasheet. 
> 
> This only affects the BIOS code that does RAM detection, so the Bochs
> BIOS code would also need to be changed accordingly.

Actually, in fact I'm interested to find out wether there are other
differences between qemu and a real 440bx-based motherboard, besides RAM
detection.

I'm asking because I'm willing to rewrite the coreboot qemu support code
based on the generic northbridge/southbridge code.

Thanks,
Cristi

-- 
Ing. Cristi Măgherușan, System/Network Engineer
Technical University of Cluj-Napoca, Romania
http://cc.utcluj.ro  +40264 401247

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Re: [Qemu-devel] Intel 440bx hardware emulation correctness

[Jordan Justen]

Cristi,

My impression is that QEMU does not focus on strict hardware
emulation.  I think it would be counter-productive to (what I see as)
QEMU's main goals ... to emulate a functional system with good
performance.

It seems that the level of hardware compatibility is driven by
software dependencies.  Essentially, if an OS driver expects the
hardware to behave a certain way, then QEMU will emulate it to achieve
compatibility.

But, since the OS's do not generally know about SPD & configuring the
chipset memory, it is easier to ignore this completely in QEMU.

-Jordan

On Sun, Jul 26, 2009 at 9:37 AM, Cristi
Magherusan<Cristi.Magherusan@net.utcluj.ro> wrote:
> On Sun, 2009-07-26 at 14:35 +0300, Cristi Magherusan wrote:
>> Hello,
>>
>>
>> Does qemu aim to completely emulate the Intel 440bx northbridge hardware
>> (and maybe other) to detail, or instead does it on purpose skip some
>> parts for the sake of simplicity?
>>
>> As an example, I've seen that the RAM parameters are written in CMOS
>> instead of doing it using SPD and some RAM control registers, as
>> documented in the 440 datasheet.
>>
>> This only affects the BIOS code that does RAM detection, so the Bochs
>> BIOS code would also need to be changed accordingly.
>
> Actually, in fact I'm interested to find out wether there are other
> differences between qemu and a real 440bx-based motherboard, besides RAM
> detection.
>
> I'm asking because I'm willing to rewrite the coreboot qemu support code
> based on the generic northbridge/southbridge code.
>
> Thanks,
> Cristi
>
> --
> Ing. Cristi Măgherușan, System/Network Engineer
> Technical University of Cluj-Napoca, Romania
> http://cc.utcluj.ro  +40264 401247
>