ECS Chipset — A600 / A3000 / A500+

Overview

The Enhanced Chip Set (ECS) is a significant revision of OCS, shipping from 1990 onward. It adds 2 MB Chip RAM addressing, programmable display timing, and extended registers while maintaining full backward compatibility with OCS software.

Chip Summary

Chip	Part	Changes from OCS
Super Agnus	MOS 8372A	Addresses 2 MB Chip RAM, extended DMA window
ECS Denise	MOS 8373	BPLCON3, border blank, programmable sync
Paula	MOS 8364	Unchanged

File	Topic
chipset_ecs.md	Super Agnus and ECS Denise internals
ecs_registers_delta.md	New/changed registers vs OCS
productivity_modes.md	Multiscan/productivity display modes
gary_system_controller.md	Gary & Fat Gary — system controller gate array: address decode, bus arbitration, AutoConfig, SCSI/FPU glue, chip variants, runtime detection, antipatterns, FPGA timing
Gayle IDE & PCMCIA	A600 Gayle: IDE and PCMCIA (shared with A1200)
ecs_sprites.md	ECS sprite enhancements: border sprites, independent resolution (SPRES), color bank
chip_ram_expansion.md	2 MB Chip RAM with Super Agnus

ECS vs OCS — Key Differences

Feature	OCS	ECS
Max Chip RAM	1 MB (Fat Agnus)	2 MB (Super Agnus)
Display sync	Fixed NTSC/PAL	BEAMCON0 — programmable
Bitplane scroll	4-bit (BPLCON1)	Extended (ECS Denise)
Border blank	No	BPLCON3 border control
Hires sprites	No	ECS Denise extended sprite control
DMA window	Smaller	Extended: wider bitplane fetch

Identifying ECS at Runtime

#include <exec/execbase.h>

struct ExecBase *SysBase = *((struct ExecBase **)4);
/* AttnFlags does not directly identify chipset */

/* Use graphics.library GfxBase->ChipRevBits0 */
#include <graphics/gfxbase.h>
struct GfxBase *GfxBase = (struct GfxBase *)OpenLibrary("graphics.library", 0);
if (GfxBase->ChipRevBits0 & GFXB_BIG_BLITTER) { /* ECS+ */ }
if (GfxBase->ChipRevBits0 & GFXB_HR_AGNUS)    { /* Super Agnus */ }
if (GfxBase->ChipRevBits0 & GFXB_HR_DENISE)   { /* ECS Denise */ }

Machines Using ECS

Model	Notes
A3000	Super Agnus + ECS Denise; 68030; SCSI; Zorro III
A500+	Super Agnus (1 MB variant); ECS Denise; no IDE
A600	Super Agnus (1 MB variant); ECS Denise; Gayle; IDE; PCMCIA
A2000 (late)	Some late rev boards shipped with ECS chips

References

ADCD 2.1 Hardware Manual — ECS extension chapters
NDK39: graphics/gfxbase.h — ChipRevBits0 flags
Amiga Hardware Reference Manual 3rd ed. — ECS appendix

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