[LinuxBIOS] raminit.c

I hope someone can clarify this for me. The main purpose of the  
raminit.c file is to:

a) setup the most minimal northbridge memory registry
b) detect spd to find memory parimeters
c) set the spd parimeters in the northbridge memory registry
d) startup memory

Is this correct??
The main question I have is how do I know which of the northbridge  
memory registers need to be setup on initially?? If they are to use  
their default values to I even need to include them?? Or should I just  
set them all up??
Please Help me out here.

Thanks - Joe

[Stefan Reinauer]

* [e-mail]  [070322 00:48]:
> a) setup the most minimal northbridge memory registry
> b) detect spd to find memory parimeters
> c) set the spd parimeters in the northbridge memory registry
> d) startup memory
>
> Is this correct??

a) sounds suspicious. No "minimal" setup, but rather "those registers of
   the memory controller that don't have to be setup via c.
> The main question I have is how do I know which of the northbridge  
> memory registers need to be setup on initially?? If they are to use  
> their default values to I even need to include them?? Or should I just  
> set them all up??

Heh. :-) That is the tricky part. You have to read the docs, and try to
understand, and you can compare the registers to those of the legacy
bios.

Some chipsets have a "bios porting guide", but except for AMD chipsets,
they are usually hard to get.

Stefan

Quoting Stefan Reinauer :
> [e-mail]  [070322 00:48]:
> > a) setup the most minimal northbridge memory registry
> > b) detect spd to find memory parimeters
> > c) set the spd parimeters in the northbridge memory registry
> > d) startup memory
> >
> > Is this correct??
>
> a) sounds suspicious. No "minimal" setup, but rather "those registers of
>    the memory controller that don't have to be setup via c.
> > The main question I have is how do I know which of the northbridge
> > memory registers need to be setup on initially?? If they are to use
> > their default values to I even need to include them?? Or should I just
> > set them all up??
>
> Heh. :-) That is the tricky part. You have to read the docs, and try to
> understand, and you can compare the registers to those of the legacy
> bios.
>
> Some chipsets have a "bios porting guide", but except for AMD chipsets,
> they are usually hard to get.
>
> Stefan

Ok, that makes sense. I was able to get the all of the memory register  
settings via the legacy bios. So should I just set the ones that are  
not the default values? Also, is there a "bios porting guide" for  
intel chipsets??

Thanks again - Joe
>

[Stefan Reinauer]

* [e-mail]  [070322 01:01]:
> Ok, that makes sense. I was able to get the all of the memory register  
> settings via the legacy bios. So should I just set the ones that are  
> not the default values?

yes, basically. In the beginning you can just start by poking the legacy
bios values in there.

Then, if that works, start replacing those that need to be set based on
SPD values by the values you calculated.

This way you have several smaller problems instead of a big one
> Also, is there a "bios porting guide" for  
> intel chipsets??

yes. But you need an NDA, and to get that you need a use case (many
machines involved -> Business for Intel), which will be hard to get
for older hardware.

Stefan

[Stefan Reinauer]

* Stefan Reinauer  [070322 01:40]:
> > Ok, that makes sense. I was able to get the all of the memory register  
> > settings via the legacy bios. So should I just set the ones that are  
> > not the default values?
>
> yes, basically.

Forget what I said. Eric is right. You should set up all registers, not
just the changing ones.

[e-mail] writes:
> I hope someone can clarify this for me. The main purpose of the  
> raminit.c file is to:
>
> a) setup the most minimal northbridge memory registry
> b) detect spd to find memory parimeters
> c) set the spd parimeters in the northbridge memory registry
> d) startup memory
>
> Is this correct??

Basically.
> The main question I have is how do I know which of the northbridge  
> memory registers need to be setup on initially?? If they are to use  
> their default values to I even need to include them??

Never trust hardware to have default values, if you can help it.
Hardware engineers like to leave registers floating (so they
can take random values) if the don't absolutely have to initialize
them.  Plus there are other cases like reset and very short
power offs where the capacitance in registers can help them hold
a value.
> Or should I just set them all up??

Yes.  If you know a good value for the register to have you should
set it up.

Also carefully test it remembering that people are fallible so the
is probably something missed or slightly incorrect in the documentation.

Eric