91
I/O Address (hex)
Size
Assignment
0377 write
1 byte
Floppy drive channel 2 command
0377 bit7 read
1 bit
Floppy drive channel 2 disk change status
0377 bit0:6
7 bits
Secondary IDE channel status
0378 – 037F
8 bytes
Parallel port 1
03B4 – 03B5
2 bytes
Add-in card; VGA
03BA
1 byte
Add-in card; VGA
03BC – 03BF
4 bytes
Parallel port 3
03C0 – 03CA
11 bytes
Add-in card; VGA
03CC
1 byte
Add-in card; VGA
03CE – 03CF
2 bytes
Add-in card; VGA
03D4 – 03D5
2 bytes
Add-in card; VGA
03DA
1 byte
Add-in card; VGA
03E8 – 03EF
8 bytes
COM 3
03F0 – 03F5
5 bytes
Floppy drive channel 1
03F6
1 byte
Primary IDE channel command
03F7 write
1 byte
Floppy drive channel 1 command
03F7 bit7 read
1 bit
Floppy drive channel 1 disk change status
03F7 bit0:6 read
7 bits
Primary IDE channel status
03F8 – 03FF
8 bytes
COM 1
0CF8 – 0CFB
4 bytes
PCI configuration address registers (DW access)
0CFC – 0CFF
4 bytes
PCI configuration data registers
FF00 – FF07
8 bytes
IDE bus master registers
FFA0 – FFA7
8 bytes
Primary IDE bus master registers
FFA8 – FFAF
8 bytes
Secondary IDE bus master registers
Memory Addresses
Memory Address
Range
Size
Description
0K – 512K
00000000 – 0007FFFF
512K
DOS conventional memory
512K – 640K
00080000 – 0009FFFF
128K
DOS conventional memory or
memory hole
640K – 768K
000A0000 – 000BFFFF
128K
VGA memory and BIOS
768K – 896K
000C0000 – 000DFFFF
128K
Expansion card BIOS and buffer
896K – 1024K
000E0000 – 000FFFFF
128K
System BIOS
1024K – 15360K
00100000 – 00EFFFFF
15.36M
Main memory
15.36M – 16.384M
00F00000 – 00FFFFFF
1024K
ISA memory hole (optional)
16.384M –
Top of memory
01000000 – Top of memory
xxxx
Main memory
