[flashrom] testing DELL Dimension 4100

[Bertho Grandpied]

--- Stefan Tauner <stefan.tauner at ....at> wrote :

> Czerno wrote ! 
>> Testing Dell Dimension 4100 : Pentium III and Intel 815
>> (82815 + 82801BA, ICH2)
>> This chipset should be supported IIUC, but flash chip
>> is not detected :(

>> question arises, is that Intel chipset variant supported or
>> is it not ?
 
 
> (intel) chipsets can be configured by the bios in a lot of ways and
> since some configuration options are directly targeted at restricting
> flash chip access, chipset support as defined by flashrom/us does not
> necessarily mean that flashrom can actually access the flash chip
> freely. most of the time this does only affect writing.

 
>> WARNING: Setting Bios Control at 0x4e from 0x02 to 0x03
> on ICH2 failed.
>> New value is 0x02.
>> FAILED!
 
> this is telling us that we failed to set bit 0 of BIOS_CNTL.
> this bit is named "BIOS Write Enable"...
> the reason why we failed to set it, is that bit 1 is also set, which
> indicates that the BIOS will be called whenever one sets bit 0.

That register, I gather, would be configuration register 4e in the ISA (South) bridge, right? Thru which mechanism would an attempt to change that bit "call the BIOS", as you put it ? SMI ? I'm not familiar with Intel chipsets - do you have an URL for the datasheet thereof please ?


> obviously in this machine (and usually always) the BIOS then just
> unsets the bit again... no flash writes possible without
> telling the
> BIOS to stop this behavior... which is not documented.

Well, I could try to find out by inspection of Dell's BIOS updater. 
However as you remarked, the locking bit is for writes only and wouldn't prevent flashrom from reading Flash's contents, even less prevent Flashrom from detecting the flash chip. 

> This does however not explain why we do not find a flash
> chip. Most
> probably it is not supported yet. The EC (SMSC) might be
> involved too.
> If you care please tell us the markings on the flash chip.

It might take some time before I find an opportunity to inspect that board. Meanwhile, there's no software way to probing harder ?

> Support for
> reads should be easy to add, but writes won't happen at
> least on that  board...

Except, perhaps, by finding the secret handshake through the 'reversing' of Intel/Dell BIOS updaters. 
I suspect Dell used/customised a solution provided to them by Intel.
What's more, the unlocking procedure could apply to a wide range of boards (natural lazyness...) - don't you have keys already to comparable bioses and mobos ?  

Regards...

-- 
Czerno