[coreboot] [flashrom] unusual SST39SF020 chip

Andriy Gapon avg at icyb.net.ua
Thu May 15 10:49:26 CEST 2008

on 15/05/2008 05:32 Carl-Daniel Hailfinger said the following:
> Hi Andriy,
> On 14.05.2008 22:30, Andriy Gapon wrote:
>> First of all, I have a very rough (and ugly!) patch that makes flashrom 
>> work on FreeBSD. I tried it for reading BIOS image and it worked.
> Can you mail the patch to the list? We want flashrom to be
> cross-platform and will try to merge the patch or at least a variant of it.

The diff is attached.
But it is really very ugly and hackish.
The most noisy change is that outb has different order of arguments on 
Linux and FreeBSD.

>> I have an old system with MP2-BX-X, please see some description here:
>> http://www.geocities.com/SiliconValley/3686/delta_mp2.html
>> It is based on 440BX chipset.
>> Visually I was able to identify that BIOS flash chip is SST39SF020, but 
>> flashrom didn't initially recognize it.
>> Some debugging showed that it has JEDEC ids 0x25 for vendor and 0xE5 for 
>> device. Very unusual. So I decided to let you know.
> The JEDEC vendor ID 0x25 can mean any of the following companies:
> - Tristar
> - Zarlink/Mitel
> - Chameleon systems
> - Kingmax Semiconductor
> - Phyworks
> - Power-One
> None of the companies above are in the BIOS flash market AFAICS.
> Probably this is just a strange reading of real flash contents at ID
> offsets.
>> The data that flashrom read are very similar to the data in vendor 
>> provided bios .bin. There are differences in a chunk of about 12k size, 
>> I guess this is where bios stored some config data.
> Can you hexdump the first 8 bytes of the bios.bin you read back from
> your chip?

Here it is (16 bytes):
00000000  25 e5 2d 6c 68 35 2d 52  16 00 00 9e 1f 00 00 02

It does include -lh5- signature. I was even able to split it into 
several chunks on that signature, decompress the chunks and even 
disassemble some pieces. Interestingly enough this BIOS contains 
original.tm1 file in addition to original.tmp and the former seems to be 
a trailer of the latter.

Hmm, I see that 25 e5 is present here. So it might mean that my ported 
code didn't properly enable flash chip communication?

Andriy Gapon
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