Schauen Sie sich dieses Intele Handbuch:
http://www.intel.com/content/dam/www/public/us/en/documents/manuals/64-ia-32-architectures-software-developer-vol-3a-part-1-manual.pdf
Geht zu Seite 9-6, und nachfolgenden Seiten, alles beschreibt den anfänglichen Startmodus der CPU. Der erste Befehl geholt wird von ffffff00 (die das ROM BIOS fest verdrahtet):
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.
Und zu diesem Zeitpunkt immer noch in Erinnerung es Realmode ist:
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).
und dann weiter sehen, in Figur 9- 3, ist der Speicherort von 64K Speicher - von ffffffff zu ffff0000 und angegeben, gibt es EPROM oder System BIOS und somit nicht RAM.
Perfekt, danke! –