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Ilia Sharin 21751c0025 docs(amiga): complete AmigaOS 3.1/3.2 developer reference — 172 files across 17 sections

Comprehensive technical documentation covering:
- Hardware: OCS/ECS/AGA custom chip registers, Copper & Blitter deep dives
- Boot sequence: cold boot through startup-sequence
- Binary format: HUNK executable spec, relocation, debug info
- Linking & ABI: .fd files, LVO tables, register calling conventions
- Exec kernel: tasks, interrupts, memory, signals, semaphores
- AmigaDOS: file I/O, FFS/OFS layout, CLI/Shell scripting
- Graphics: planar bitmaps, Copper programming, HAM/EHB modes
- Intuition: screens, windows, IDCMP, BOOPSI
- Devices: trackdisk, SCSI, serial, timer, audio, keyboard
- Libraries: utility, expansion, IFFParse, locale, ARexx
- Networking: bsdsocket API, SANA-II, TCP/IP stack comparison
- Toolchain: GCC, vasm/vlink, SAS/C, NDK, debugging
- Reverse engineering: IDA/Ghidra setup, compiler fingerprints, case studies
- CPU & MMU: 68040/060 emulation libs, PMMU, cache management
- Driver development: SANA-II, Picasso96/RTG, AHI audio

All files include breadcrumb navigation. No local paths or proprietary content.

2026-04-23 12:17:35 -04:00

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← Home · Graphics

Display Modes — Display Database, ModeID, Monitor Specs

Overview

OS 3.0+ provides a display database that abstracts monitor/chipset capabilities. Applications query available modes by ModeID rather than hardcoding HIRES/LACE flags.

ModeID Format

A ModeID is a ULONG:

bits 31–16: Monitor ID
bits 15–0:  Mode within that monitor

ModeID	Name	Resolution
`$00000000`	LORES	320×256 (PAL) / 320×200 (NTSC)
`$00008000`	HIRES	640×256/200
`$00000004`	LORES-LACE	320×512/400
`$00008004`	HIRES-LACE	640×512/400
`$00080000`	SUPERHIRES	1280×256 (ECS+)
`$00080004`	SUPERHIRES-LACE	1280×512
`$00039000`	DBLPAL-LORES	320×256 (AGA scan-doubled)
`$00039004`	DBLPAL-HIRES	640×256 (AGA)
`$00011000`	DBLNTSC-LORES	320×200 (AGA)

Querying the Display Database

/* graphics.library 39+ */
ULONG modeID = INVALID_ID;
struct DisplayInfo di;
struct DimensionInfo dims;

while ((modeID = NextDisplayInfo(modeID)) != INVALID_ID) {
    if (GetDisplayInfoData(NULL, (UBYTE *)&di, sizeof(di),
                           DTAG_DISP, modeID)) {
        if (GetDisplayInfoData(NULL, (UBYTE *)&dims, sizeof(dims),
                               DTAG_DIMS, modeID)) {
            Printf("ModeID $%08lx: %ldx%ld, %ld colours\n",
                    modeID,
                    dims.Nominal.MaxX - dims.Nominal.MinX + 1,
                    dims.Nominal.MaxY - dims.Nominal.MinY + 1,
                    1 << di.NotAvailable ? 0 : dims.MaxDepth);
        }
    }
}

Best Mode Selection

ULONG bestMode = BestModeIDA((struct TagItem[]){
    { BIDTAG_NominalWidth,  640 },
    { BIDTAG_NominalHeight, 480 },
    { BIDTAG_Depth,         8 },
    { TAG_DONE, 0 }
});

References

NDK39: graphics/displayinfo.h, graphics/modeid.h
ADCD 2.1: NextDisplayInfo, GetDisplayInfoData, BestModeIDA

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