pc386 BSP on board with UMA

[Chris Johns]

Joel Sherrill wrote:
> On 12/09/2009 06:16 PM, Chris Johns wrote:
>> Joel Sherrill wrote:
>>   
>>>      
>> Interesting manual. Seems to assume you know what TSEG, SMM etc is.
>>
>>    
> I found SMM .. System Management Mode.  (I think)

Yes found this. What about TSEG and CSEG ?

>>> The memory sizing algorithm finds 1007MB on this board.
>>>      
>> What memory sizing code is this ?
>>
>>    
> startup/bspgetworkarea.c .. should be same code that
> has existed in the bsp for ages.
> 
> 
> FWIW zero'ing the workspace is what made it write to
> this memory.  Normally we don't need 1GB of RAM. :)
> 
>>> But
>>> if you clear all of that memory, the system locks up. If I
>>> decrease that to 1004MB, things work. My reading of the
>>> above is that we shouldn't touch the last 64MB RAM.
>>>
>>> Does that make sense? Is there some way to know this?
>>>
>>>      
>> I have not followed in detail the size you need to leave, but I would
>> have thought the BIOS would have taken this into account for you.
>>    
> Does that mean the multiboot info would be right?
> 

I would assume so. Given the manual states the BIOS can turn on or off 
the various memory regions it must know and I assume the BIOS tell the 
boot loader the set up and this ends up in the multiboot data.

> The sizing code has 3 options:
> 
> + RamSize from linkcmds

No given the flexible memory arrangement in a PC.

> + dynamic sizing

Too hard and it is the job of the BIOS.

> + multiboot info.

Yes.

> 
> I think the code is structured such that it takes
> the multiboot, then overwrites it with either the
> sizing or hardcoded number.
> 
> Hmmm... this code looks different on the head vs 4.9
> but the sizing algorithm is the same.  I will have to look
> at it in detail tomorrow to see if 4.9 might have given higher
> priority to the multiboot info.
> 
> What do you think?
> 

Why would you want to override the multiboot values ?

Chris

> --joel
>> Chris
>>
>>   
>>> Help... :)
>>>      
>>
>>
>>    
>