[LinuxBIOS] RAM controller breakage?

Richard Smith smithbone at gmail.com
Sat Nov 11 21:22:29 CET 2006

Tom Sylla wrote:

>> I'm just a bit curious - are there settings/registers in northbridges
>> which can seriously brick a mainboard and/or RAM (physically) if abused
>> properly?
> There is nothing you can do from software to physically harm SDR, DDR, 
> or DDR2 devices.

100% agree with Tom.  I suppose if you somehow tickle some crazy bug to
  make the controller output the wrong voltage you could do something
bad to the rams but the chances of that are so low they aren't even
worth considering.  Remember thats a really mature chipset.

I've put all manner of wrong settings in those chips and during the
development of the Bitworks/IMS board we did all sorts of "Bad" things
to the ram and it kept on plugging.

So I think you are safe.

Thinking about this brings back a few memories.

1) I found in my testing that you can do things to the north bridge that
will crash it in such a way that a reset does not fully fix.  It's very
sneaky, things just start behaving really weird and your code just seems
to start failing for no good reason.  But not so bad as to suspect that
its hardware.  Especially if you are doinking with the register settings
at the time.

The only fix is to _remove_ power from the board.  And on the ASUS I
seem to remember having to remove the CMOS battery as well.
(Bitworks/IMS had no battery)
So I recommend you remove the battery and power cycle frequently.

2) The 66Mhz/100Mhz operation of the front side bus is controlled via a
jumper.  The Bitworks board however was never qualified to run at
100Mhz.  So all the settings are for 66Mhz.  If you run with the 66Mhz
drive settings yet have the jumper set to 100Mhz you are in for a lot of
frustration.  Just depends on the quality of your ram and the board
I recommend that you do all you development with 66Mhz and then work out
the 100Mhz settings after you have the code working.  I can't help much
with the 100Mhz settings.  You will need to dump a Factory BIOS set to
100Mhz and compare how they setup the drive settings.

Richard A. Smith

More information about the coreboot mailing list