Bricking (and unbricking) your board.

[Myles Watson]

I was surprised how easy it was to brick my board.  These ideas might
be useful to somebody:

Before you start messing with PCI & I/O values that might keep their state:

- have a lspci -vvvxxx from the factory BIOS
- record as much of the boot process from the factory BIOS as possible

I wanted to collect the bit masks from my factory BIOS, so I modified
the filter to return 0x0 and then 0xffffffff for the PCI registers.
That way I could see which bits were being changed.  After some of the
registers were changed, I couldn't boot the board with Coreboot or the
factory BIOS.  I used SerialICE to set the PCI values to what they
were in a saved run of the factory BIOS, and it booted again.

Thanks,
Myles

[Peter Stuge]

Myles Watson wrote:
> I used SerialICE to set the PCI values to what they were in a saved
> run of the factory BIOS, and it booted again.

Which device were the registers in?

//Peter

[Rudolf Marek]

Hi,

Maybe you messed up the power well powered registers? Unplugging the AC power 
might help,

Thanks,
Rudolf

[Joseph Smith]

On 07/06/2010 05:58 PM, Myles Watson wrote:
> I was surprised how easy it was to brick my board.  These ideas might
> be useful to somebody:
>
> Before you start messing with PCI&  I/O values that might keep their state:
> have a lspci -vvvxxx from the factory BIOS
> record as much of the boot process from the factory BIOS as possible
>
> I wanted to collect the bit masks from my factory BIOS, so I modified
> the filter to return 0x0 and then 0xffffffff for the PCI registers.
> That way I could see which bits were being changed.  After some of the
> registers were changed, I couldn't boot the board with Coreboot or the
> factory BIOS.  I used SerialICE to set the PCI values to what they
> were in a saved run of the factory BIOS, and it booted again.

Wow that is interesting. Even after you disconnected power (ATX 
connector) and cmos battery it would still keeps those values?

[Myles Watson]

On Tue, Jul 6, 2010 at 4:00 PM, Peter Stuge  wrote:
> Myles Watson wrote:
> > I used SerialICE to set the PCI values to what they were in a saved
> > run of the factory BIOS, and it booted again.
>
> Which device were the registers in?

The HyperTransport controller and the SMBUS controller, but there
could be more.  I stopped trying to get all the masks correctly when I
saw how easy it was to break it.

Thanks,
Myles

[Myles Watson]

> Wow that is interesting. Even after you disconnected power (ATX connector)
> and cmos battery it would still keeps those values?

Since I could recover with SerialICE I didn't try it.  I was surprised
that the factory BIOS wouldn't set the values correctly, though.

Thanks,
Myles

[Joseph Smith]

On 07/06/2010 06:39 PM, Myles Watson wrote:
> > Wow that is interesting. Even after you disconnected power (ATX connector)
> > and cmos battery it would still keeps those values?
>
> Since I could recover with SerialICE I didn't try it.  I was surprised
> that the factory BIOS wouldn't set the values correctly, though.

I'm not. I have seen some factory bios' that have a sequence in the 
begining that goes through and writes a bunch of pci registers to their 
default values and some factory bios' that don't. The devices that keep 
those values must be strapped to a capacitor or the cmos battery.