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Date: Fri, 14 Jul 2006 15:30:08 +0530
From: sudheer <urwithsudheer@gmail.com>
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To: Sivasankar Chander <siva.ilugc@gmail.com>
Subject: Re: [Ilugc] help regarding powerpc and vga card
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Hello Sivasankar,

sudheer wrote:

> Hello Sivasankar,
>
> Sivasankar Chander wrote:
>
>>
>>
>> On 7/13/06, *sudheer* <urwithsudheer@gmail.com 
>> <mailto:urwithsudheer@gmail.com>> wrote:
>>
>>
>>
>>     Anyone please help me if i am missing anything.
>>
>>     All PCI VGA cards for use on x86 PCs have a ROMscan BIOS
>> extension on them. This initializes the card after POST - basically,
>> the motherboard BIOS transfers control to the BIOS on the
>> PCI VGA card, which then initializes itself. If control is not
>> transfered to the VGA BIOS on the card, the VGA controller
>> stays isolated and will not respond to PCI device enumeration,
>> etc. 
>
I have a doubt here. How does the processor know that the card  sitting 
here is a vga card
and control should be transfered to initialize it.  I think it can know 
that it is a vga card only by reading the config space .
And bios is necesary for vga card to work in its normal way. Is it 
necesary for bios to be initialised to get detected.
Please correct me if i am wrong.

>> This is actually part of the PC-98 spec., which allows
>> multiple VGA controllers to co-exist on the PCI and/or AGP
>> bus.
>>
>>    On a PowerPC system, the ROMscan BIOS cannot execute
>> (because it has x86 instructions in it), so there will be an alternate
>> way to initialize the VGA controller so that it can respond to the
>> PCI enumeration, etc. However, that method will be card/controller
>> specific - neither the card manufacturer nor ATI may ever have
>> released the specs for how this is done. Usually, it will be through
>> hidden memory-mapped IO (MMIO) registers on the VGA controller
>> chip, but there are numerous proprietary ways to implement this,
>> most of it being undocumented or controller-specific.
>
>
> Thanks for your information.
> Could anyone please suggest me which  vga card i need to buy so that 
> it can be supported
> with powerpc boards and available in the market. Or can i have any 
> other alternative solution .
>
> Thanks  & Regards
> Sudheer
>
>>
>> (Lots of things are taken for granted in the x86 PC world, which
>> are actually very complex and difficult-to-implement protocols.
>> That's one of the reasons why all the alternative PC processor
>> architectures have failed over the last 20 years).
>>
>> -Siva
>
Thanks & Regards
Sudheer
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