ще потърся за Правец ,още не съм намерил
иначе за XT BIOS ... ето какво пише
Expansion Card Hardware Expansion cards are likely to provide the following hardware (that BIOS is likely to initialize if found) as well:
6845 CRT Controller (0x3D4-5 Color, 0x3B4-5 Mono)
MM58167 RTC (0x240, 0x300, 0x340- Found by trial and error)
TTL Glue logic for Color and Mono adapter configuration (0x3D4-0x3DF Color, 0x3B4-0x3BF Mono)
TTL Glue logic for Line Printer Terminal (LPT) (0x3BC, 0x378, 0x278, ?)
TTL Glue logic for Game Control Adapter (0x201)
16550 UART for Serial Communications (COM) (0x3F8, 0x2F8, 0x3E8, 0x238)
765 Floppy Disk Controller (0x3F2 Glue logic, 0x3F4-0x3F5 Controller)
VGA VLSI chip (BIOS is provided by controller- PC BIOS simply needs to jump to setup routine)
Xebec-standard XT hard disk controller (BIOS is provided by controller- PC BIOS simply needs to jump to setup routine)
Ethernet card (BIOS is provided by card- PC BIOS simply needs to jump to setup routine)
Most hardware is exposed through x86 port-mapped I/O ports. Memory-mapped I/O is reserved for BIOS ROM chips, extra memory and the frame buffer.