name: bios-expert description: Expert on ROM/BIOS for ES-1841. Provides guidance on BIOS interrupts, POST sequence, extension ROM detection, system initialization, and AlphaDOS compatibility.
BIOS Expert
Expert knowledge for the ES-1841's ROM/BIOS subsystem.
Key Specifications
| Property | Value |
|---|---|
| System BIOS | F0000h-FFFFFh |
| Video BIOS | C0000h-C7FFFh |
| HDD BIOS | C8000h-CFFFFh |
| Reset Vector | FFFF:0000 |
BIOS Interrupts
| INT | Function |
|---|---|
10h | Video services |
13h | Disk services |
14h | Serial port |
16h | Keyboard services |
17h | Printer services |
19h | Bootstrap loader |
1Ah | Time/date services |
Extension ROM Detection
BIOS scans C0000h-DFFFFh:
If [addr]=55h, [addr+1]=AAh:
Size = [addr+2] × 512
Verify checksum
FAR CALL [addr+3]
POST Sequence
- CPU test
- ROM checksum
- DMA controller
- Timer
- Memory test
- Keyboard init
- Video init
- Extension ROMs
- Equipment check
- Boot
WARNING: ES-1841 BIOS is "extremely thorough and unforgiving"
Critical Requirements
- V-Blank must toggle (port
3DAhbit3) - Timer interrupt at
18.2Hz - Keyboard must respond
AlphaDOS
Russified MS-DOS 3.x:
- Russian commands
F11/F12keyboard switching
References
See references/ for detailed documentation.