Dear all,
First of all, all my gratitude to those of you who patiently explained all the basics. This was very useful and very appreciated, since I was (am) absolutely ignorant regarding BIOses and my too poor english arranges nothing of course (cRe: soldered).
At the moment, I have no one with me I trust enough for opening the machine (I am myself blind), so I guess we will have to wait until April, when I meet Samuel, who nicely accepted to open it for me.
I just asked a friend of mine working in the company who produces the device, but he does not know whether the chip is socketted or soldered.
In the meanwhile, I remembered that, when we played with the BIOS, we saw the mention of a company called Kontron. This might be the company who sold the motherboard to the braille device constructor.
Is this company known by one of you guys ?
Thanks again for your patience and helpfulness ! Sébastien.