[LinuxBIOS] does reinitializing memory controller destroy all the data in ram?

[RusH]

Im sorry that Im again posting not exactly on the topic of linuxbios,
but I know that people reading this list have the knowledge  about the
subject that im interested in.

Does reinitializing memory controler destroy all the data in ram?
Lets say I boot the computer, bios sets up the memory controller, then
runs bootloader, then my code. Now my code (using CAR) once again
reinitializes memory controller (sets up everything just like the
bios, only changes timings), will all the data be in ram after this?
or will it get wiped out/destroyed?

At first I was hoping that Bios initializes memory controller only on
cold boot, but it does it on soft ones too :(, my hope now lies in
attaching a bios module to  reinitialize it after the bios is
executed. I want my code to be able to set all the timings. I can do
it for tRCD tRP tRAS, but almost all controllers dont like tCAS
changes and will simply hang up the computer (KT133 and AMD64 to name
a few).

It would be a lot simplier if linuxbios could just boot XP crap :(

[LinuxBIOS] does reinitializing memory controller destroy all the data in ram?

[RusH]

On 6/10/07, RusH  wrote:
> It would be a lot simplier if linuxbios could just boot XP crap :(

umm no it wouldnt, I dont know what I was thinking :)

Im asking about reinitialization because I want to implement it in
Memtest (memtest.org). I want to be able to setup memory controler the
way I like and continue the test. Memtest is big (>100KB) and Im
affraid it wont fit in cache so i need some real ram. Thats where the
'jump to CAR, reinitialize controller, jump back to ram' idea comes
from. Is it doable?

[Bari Ari]

RusH wrote:
> Does reinitializing memory controler destroy all the data in ram?

Yes.

You might be able to get away with some minor changes to memory 
controller settings, but nothing would be guaranteed by the chipset 
maker to be stable. Chipsets  typically aren't designed to be 
reinitialized while saving the data in RAM at the same time. The data in 
RAM is indeterminate until after the memory controller is fully initialized.

-Bari

[LinuxBIOS] does reinitializing memory controller destroy all the data in ram?

[Carl-Daniel Hailfinger]

On 10.06.2007 06:40, RusH wrote:
> Im asking about reinitialization because I want to implement it in
> Memtest (memtest.org). I want to be able to setup memory controler the
> way I like and continue the test. Memtest is big (>100KB) and Im
> affraid it wont fit in cache so i need some real ram. Thats where the
> 'jump to CAR, reinitialize controller, jump back to ram' idea comes
> from. Is it doable?

Why not run Memtest from graphics card RAM? A few years ago, graphics
card RAM was really low quality, so periodic checksumming of any
software running there might be necessary.
> Does reinitializing memory controler destroy all the data in ram?

Depends. Some embedded systems (like the OLPC laptop) put memory
into self-refresh for suspend-to-RAM and reinitialize the memory
controller on resume without losing any contents. However, I
wouldn't count on that for any recent non-embedded x86 system.

Regards,
Carl-Daniel

[LinuxBIOS] does reinitializing memory controller destroy all the data in ram?

[RusH]

On 6/10/07, Carl-Daniel Hailfinger  wrote:
> On 10.06.2007 06:40, RusH wrote:
> > Im asking about reinitialization because I want to implement it in
> > Memtest (memtest.org). I want to be able to setup memory controller the
> > way I like and continue the test. Memtest is big (>100KB) and Im
> > afraid it wont fit in cache so i need some real ram. That's where the
> > 'jump to CAR, reinitialize controller, jump back to ram' idea comes
> > from. Is it doable?
>
> Why not run Memtest from graphics card RAM? A few years ago, graphics
> card RAM was really low quality, so periodic checksumming of any
> software running there might be necessary.

Date: Wed, 30 May 2007 18:57:44 +0200
From: RusH 
To: [e-mail]
Subject: using Graphics card ram as actual ram?
Message-ID:

so yes, i was thinking about it :)
> > Does reinitializing memory controller er destroy all the data in ram?
>
> Depends. Some embedded systems (like the OLPC laptop) put memory
> into self-refresh for suspend-to-RAM and reinitialize the memory
> controller on resume without losing any contents. However, I
> wouldn't count on that for any recent non-embedded x86 system.

What about AMD64 controller? I know I can change a lot of timings on
it, but changing tCAS is not possible without reinitializing, that's
why I want to be able to reinitialize on the fly.

I read somewhere that reinitializing (memory allready set up earlier)
without touching the mappings would be ok, but I want to be sure
before starting coding (easier to ask than sit on it a good week and
wonder why it doesnt work).

I guess I'll have to check for myself. All I got now is two boards
with KT133 chipset, and that doesnt look to be supported (but
PLE133/CLE266 are similar, so maybe that code will do).