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Peripherals and models description improved and expanded
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Ilia Sharin
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19 changed files with 1752 additions and 275 deletions
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@ -6,46 +6,102 @@
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The Amiga uses a **24-bit physical address bus** on OCS/ECS machines (68000/68020 effective), giving 16 MB of addressable space. AGA machines with 68030/040 and 32-bit-clean software can address the full 4 GB, but Chip RAM and custom registers remain in the lower 16 MB.
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## Memory Map — 24-bit (OCS/ECS, A500/A600/A3000)
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## Memory Map — 24-bit (OCS/ECS: A1000, A500, A500+, A2000, A600, A3000, CDTV)
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```
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$000000–$1FFFFF Chip RAM (max 2 MB on ECS, 512 KB on OCS A500)
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$200000–$9FFFFF Fast RAM (expansion via Zorro II autoconfig)
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$A00000–$BEFFFF Zorro II I/O space
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$BFD000–$BFDFFF CIA-B (8520, keyboard, floppy motor, disk side)
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$BFE001–$BFE1FF CIA-A (8520, parallel port, serial flags, timer)
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$C00000–$C7FFFF Slow RAM ("Ranger", DMA-visible but not fast)
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$C80000–$CFFFFF Zorro II expansion I/O (boards)
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$D00000–$D7FFFF Zorro II expansion I/O
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$D80000–$DBFFFF Reserved / board-specific
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$DC0000–$DCFFFF Real-Time Clock (MSM6242B / RF5C01A)
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$DD0000–$DEFFFF Reserved
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$DF0000–$DFFFFF Custom chip registers ($DFF000–$DFF1FE)
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$E00000–$E7FFFF Kick memory (WCS / Ranger slow RAM mirror)
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$E80000–$EFFFFF Autoconfig space (Zorro II probe)
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$F00000–$F7FFFF Extended Kickstart ROM (OS 3.1: second 256 KB)
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$F80000–$FFFFFF Kickstart ROM (512 KB mirror at top of 16 MB)
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```
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| Address Range | Size | Region |
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|---|---|---|
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| `$000000`–`$1FFFFF` | 2 MB max | Chip RAM (512 KB on OCS A500, 1–2 MB on ECS) |
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| `$200000`–`$9FFFFF` | 8 MB | Fast RAM (Zorro II autoconfig expansion) |
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| `$A00000`–`$BEFFFF` | ~2 MB | Zorro II I/O space |
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| `$BFD000`–`$BFDFFF` | 4 KB | CIA-B (8520 — keyboard, floppy motor, disk side select) |
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| `$BFE001`–`$BFE1FF` | 512 B | CIA-A (8520 — parallel port, serial flags, timers) |
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| `$C00000`–`$C7FFFF` | 512 KB | Slow RAM ("Ranger" — on Chip bus, not DMA-visible) |
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| `$C80000`–`$CFFFFF` | 512 KB | Zorro II expansion I/O (boards) |
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| `$D00000`–`$D7FFFF` | 512 KB | Zorro II expansion I/O |
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| `$D80000`–`$DBFFFF` | 256 KB | Reserved / board-specific |
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| `$DC0000`–`$DCFFFF` | 64 KB | Real-Time Clock (MSM6242B / RF5C01A) |
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| `$DD0000`–`$DEFFFF` | 128 KB | Reserved |
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| `$DF0000`–`$DFFFFF` | 64 KB | Custom chip registers (`$DFF000`–`$DFF1FE`) |
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| `$E00000`–`$E7FFFF` | 512 KB | Kick memory (WCS / Ranger slow RAM mirror) |
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| `$E80000`–`$EFFFFF` | 512 KB | Autoconfig space (Zorro II probe) |
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| `$F00000`–`$F7FFFF` | 512 KB | Extended Kickstart ROM (OS 3.1: second 256 KB) |
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| `$F80000`–`$FFFFFF` | 512 KB | Kickstart ROM (primary, mirrored at top of 16 MB) |
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## Memory Map — 32-bit (AGA, A1200/A4000)
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## Memory Map — 32-bit (AGA: A1200, A4000, CD32)
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| Address Range | Size | Region |
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|---|---|---|
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| `$000000`–`$1FFFFF` | 2 MB | Chip RAM |
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| `$200000`–`$07FFFFFF` | up to 126 MB | Fast RAM (on-board via Ramsey on A4000; trapdoor/PCMCIA on A1200) |
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| `$A00000`–`$BEFFFF` | ~2 MB | Zorro II I/O |
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| `$BFD000` | — | CIA-B |
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| `$BFE001` | — | CIA-A |
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| `$C00000`–`$CFFFFF` | 1 MB | Slow RAM / board I/O |
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| `$D80000`–`$D8FFFF` | 64 KB | IDE / Gayle (A1200/A4000) |
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| `$DA0000`–`$DA3FFF` | 16 KB | PCMCIA attribute memory (A1200) |
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| `$DC0000` | — | Real-Time Clock |
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| `$DFF000`–`$DFFFFF` | 64 KB | Custom chip registers |
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| `$E00000`–`$E7FFFF` | 512 KB | Kick mirror / WCS |
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| `$F00000`–`$F7FFFF` | 512 KB | Extended Kickstart ROM |
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| `$F80000`–`$FFFFFF` | 512 KB | Kickstart ROM |
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| `$01000000`+ | up to 1.75 GB | Zorro III expansion (32-bit, A3000/A4000 only) |
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## Per-Model Address Space Variations
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The maps above show the common layout. Several models have unique regions:
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### A1000 — Writable Control Store (WCS)
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| Address Range | Size | Region |
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|---|---|---|
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| `$F80000`–`$FFFFFF` | 512 KB | **WCS RAM** — Kickstart is loaded from floppy into this RAM at boot (A1000 has no ROM-based Kickstart) |
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| `$FC0000`–`$FFFFFF` | 256 KB | Bootstrap ROM (256-byte boot loader that loads Kickstart into WCS) |
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The A1000 is the only model where Kickstart lives in **RAM**, not ROM. If power is lost, Kickstart must be reloaded from the Kickstart floppy. The WCS is write-protected after loading via a hardware latch.
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### A2000 — Zorro II Bus and CPU Slot
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| Address Range | Size | Region |
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|---|---|---|
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| `$200000`–`$9FFFFF` | 8 MB | Zorro II Fast RAM (5 expansion slots, autoconfig) |
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| `$E80000`–`$EFFFFF` | 512 KB | Autoconfig space — probed at boot for each Zorro II card |
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| CPU slot | — | Directly wired 68000 socket — accepts accelerators (GVP G-Force, A2630) |
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The A2000 is the canonical "big-box" expandable Amiga. Its 5 Zorro II slots provide 8 MB of Fast RAM address space. Some later A2000 revisions (rev 6+) support Super Agnus for 2 MB Chip RAM.
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### CDTV — CD-ROM Controller and NVRAM
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| Address Range | Size | Region |
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|---|---|---|
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| `$000000`–`$0FFFFF` | 1 MB | Chip RAM (stock, expandable to 2 MB with Super Agnus mod) |
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| `$E00000`–`$E3FFFF` | 256 KB | CDTV Extended ROM (CD filesystem, player software, DMAC) |
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| `$E40000`–`$E7FFFF` | 256 KB | CDTV Extended ROM (second bank) |
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| `$DC0000`–`$DC003F` | 64 B | Real-Time Clock (Oki MSM6242B) |
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| `$E90000`–`$E9FFFF` | 64 KB | DMAC (WD33C93 SCSI DMA controller for CD-ROM) |
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| `$F00000`–`$F3FFFF` | 256 KB | CDTV **NVRAM** (battery-backed, stores bookmarks and saves) |
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The CDTV is essentially an A500 with a CD-ROM drive, IR remote, and NVRAM in a consumer set-top box form factor. It uses the OCS chipset (original Agnus) with 1 MB Chip RAM. The DMAC at `$E90000` handles DMA transfers between the CD-ROM's SCSI interface and memory.
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### CD32 — Akiko Chip and Flash ROM
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| Address Range | Size | Region |
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|---|---|---|
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| `$000000`–`$1FFFFF` | 2 MB | Chip RAM (fixed) |
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| `$B80000`–`$B8FFFF` | 64 KB | **Akiko** custom chip (chunky-to-planar conversion, CD-ROM controller, NVRAM interface) |
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| `$DC0000`–`$DC003F` | 64 B | Real-Time Clock |
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| `$DFF000`–`$DFFFFF` | 64 KB | Custom chip registers (AGA — Alice/Lisa) |
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| `$E00000`–`$E7FFFF` | 512 KB | CD32 Extended ROM (CD filesystem, boot, CDDA player) |
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| `$F00000`–`$F7FFFF` | 512 KB | CD32 flash ROM (firmware, SysInfo) |
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| `$F80000`–`$FFFFFF` | 512 KB | Kickstart 3.1 ROM |
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The CD32's unique feature is the **Akiko** chip at `$B80000`, which provides:
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- **Chunky-to-Planar (C2P) conversion**: a hardware DMA engine that converts linear 8-bit pixel arrays to planar bitplane format — the single most sought-after feature for game ports
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- **CD-ROM controller**: handles the double-speed CD drive directly
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- **NVRAM interface**: 1 KB battery-backed storage for game saves
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> [!NOTE]
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> The CD32 has no Zorro slots, no CPU slot, no trapdoor connector, and no PCMCIA port. The only expansion path is the (rare) FMV module slot or the SX-1/SX-32 expansion unit that adds a keyboard port, IDE, and PCMCIA.
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```
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$000000–$1FFFFF 2 MB Chip RAM
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$200000–$07FFFFFF Fast RAM (on-board: 4–16 MB via Ramsey on A4000)
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Trapdoor/PCMCIA on A1200
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$A00000–$BEFFFF Zorro II I/O
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$BFD000 CIA-B
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$BFE001 CIA-A
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$C00000–$CFFFFF Slow RAM / board I/O
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$D80000–$D8FFFF IDE / Gayle (A1200/A4000)
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$DA0000–$DA3FFF PCMCIA attribute memory (A1200)
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$DC0000 RTC
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$DFF000–$DFFFFF Custom registers
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$E00000–$E7FFFF Kick mirror / WCS
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$F00000–$F7FFFF Extended ROM
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$F80000–$FFFFFF Kickstart ROM (512 KB)
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$01000000+ Zorro III expansion (32-bit, A3000/A4000 only)
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```
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## Memory Type Classification
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@ -77,16 +133,24 @@ Fast RAM is **CPU-only** — generally used for code, non-DMA data structures, a
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## Diagram
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```mermaid
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block-beta
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columns 1
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block:chip["Chip RAM\n$000000–$1FFFFF\n(DMA accessible)"]
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block:fast["Fast RAM\n$200000–$9FFFFF\n(CPU only, faster)"]
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block:zio["Zorro II I/O\n$A00000–$BEFFFF"]
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block:cia["CIA-A/B\n$BFD000/$BFE001"]
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block:slow["Slow/Ranger RAM\n$C00000–$C7FFFF"]
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block:rtc["RTC $DC0000"]
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block:custom["Custom Registers\n$DFF000–$DFFFFF"]
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block:rom["Kickstart ROM\n$F80000–$FFFFFF"]
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flowchart TB
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chip["Chip RAM<br/>$000000–$1FFFFF<br/>(DMA accessible)"]
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fast["Fast RAM<br/>$200000–$9FFFFF<br/>(CPU only, faster)"]
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zio["Zorro II I/O<br/>$A00000–$BEFFFF"]
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cia["CIA-A/B<br/>$BFD000 / $BFE001"]
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slow["Slow / Ranger RAM<br/>$C00000–$C7FFFF"]
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custom["Custom Registers<br/>$DFF000–$DFFFFF"]
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rom["Kickstart ROM<br/>$F80000–$FFFFFF"]
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chip --- fast --- zio --- cia --- slow --- custom --- rom
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style chip fill:#2d6a4f,color:#fff
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style fast fill:#1b4332,color:#fff
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style slow fill:#774936,color:#fff
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style custom fill:#e63946,color:#fff
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style rom fill:#457b9d,color:#fff
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style zio fill:#264653,color:#fff
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style cia fill:#264653,color:#fff
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```
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## Key Chip RAM Addresses
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