Intel IA-32 - Manual (Page 395)

Vol. 3A 9-21
PROCESSOR MANAGEMENT AND INITIALIZATION
Figure 9-3. Processor State After Reset
Table 9-4. Main Initialization Steps in STARTUP.ASM Source Listing
STARTUP.ASM Line
Numbers Description
From To
157 157 Jump (short) to the entry code in the EPROM
162 169 Construct a temporary GDT in RAM with one entry:
0 - null
1 - R/W data segment, base = 0, limit = 4 GBytes
171 172 Load the GDTR to point to the temporary GDT
174 177 Load CR0 with PE flag set to switch to protected mode
179 181 Jump near to clear real mode instruction queue
184 186 Load DS, ES registers with GDT[1] descriptor, so both point to the entire
physical memory space
188 195 Perform specific board initialization that is imposed by the new protected
mode
0
FFFF FFFFH
After Reset
[CS.BASE+EIP] FFFF FFF0H
EIP = 0000 FFF0H
[SP, DS, SS, ES]
FFFF 0000H
64K EPROM
CS.BASE = FFFF 0000H
DS.BASE = 0H
ES.BASE = 0H
SS.BASE = 0H
ESP = 0H