Vérifiez ce manuel Intel:
http://www.intel.com/content/dam/www/public/us/en/documents/manuals/64-ia-32-architectures-software-developer-vol-3a-part-1-manual.pdf
Aller à la page 9-6, et les pages suivantes, tout décrire le mode de démarrage initial de la CPU. La première instruction extraite est de ffffff00 (qui câblé au BIOS ROM):
The first instruction that is fetched and executed following a hardware reset is
located at physical address FFFFFFF0H. This address is 16 bytes below the
processor’s uppermost physical address. The EPROM containing the software-
initialization code must be located at this address.
Et se rappeler à ce stade, il est encore en realmode:
The CS register has two parts: the visible segment selector part and the
hidden base address part. In real-address mode, the base address is normally
formed by shifting the 16-bit segment selector value 4 bits to the left to produce a
20-bit base address. However, during a hardware reset, the segment selector in the
CS register is loaded with F000H and the base address is loaded with FFFF0000H. The
starting address is thus formed by adding the base address to the value in the EIP
register (that is, FFFF0000 + FFF0H = FFFFFFF0H).
Et puis regarde plus loin, dans la figure 9- 3, est l'emplacement de 64 Ko de mémoire - de ffffffff à ffff0000 et indiqué qu'il y a EPROM, ou bios du système, et donc pas de RAM.
Parfait, merci! –