Sega Master System (Model 1) - Revision history

Josh at 08:49, 25 May 2025

2025-05-25T08:49:26Z

← Older revision		Revision as of 09:49, 25 May 2025
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			<templatestyles src="Template:StyledTable/styles.css" />
	{{Infobox computer		{{Infobox computer
	\| name = Sega Master System (Model 1)		\| name = Sega Master System (Model 1)

Josh at 08:50, 12 May 2025

2025-05-12T08:50:29Z

← Older revision		Revision as of 09:50, 12 May 2025
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	The '''Sega Master System''' (first-generation “Model 1”, product code '''MK-2000''') is an 8-bit home console released by Sega to compete directly with Nintendo’s Famicom/NES. Re-branded from the Japan-only '''Sega Mark III''', the Master System introduced the distinctive black-and-red industrial design, a combo cartridge + “[[Sega Card]]” slot, and an edge expansion port supporting FM audio, 3-D glasses and future accessories. Although outsold by Nintendo in Japan & North America, it enjoyed major success across Europe, Brazil and Australasia, shipping an estimated '''≈ 13 million units''' worldwide.		The '''Sega Master System''' (first-generation “Model 1”, product code '''MK-2000''') is an 8-bit home console released by Sega to compete directly with Nintendo’s Famicom/NES. Re-branded from the Japan-only '''Sega Mark III''', the Master System introduced the distinctive black-and-red industrial design, a combo cartridge + “[[Sega Card]]” slot, and an edge expansion port supporting FM audio, 3-D glasses and future accessories. Although outsold by Nintendo in Japan & North America, it enjoyed major success across Europe, Brazil and Australasia, shipping an estimated '''≈ 13 million units''' worldwide.

	== 🧠 System Architecture ==		== System Architecture ==
	{\| class="wikitable styled-table" style="width:70%; text-align:center;"		{\| class="wikitable styled-table" style="width:70%; text-align:center;"
	! Sub-system !! Specification (Master System Model 1)		! Sub-system !! Specification (Master System Model 1)
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	\|}		\|}

	== 📺 Video Timing ==		== Video Timing ==
	{\| class="wikitable styled-table" style="width:70%; text-align:center;"		{\| class="wikitable styled-table" style="width:70%; text-align:center;"
	! Parameter !! NTSC !! PAL		! Parameter !! NTSC !! PAL
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	\|}		\|}

	== 🔌 Edge-Connector Pin-out ==		== Edge-Connector Pin-out ==
	=== 50-pin Cartridge Bus (looking into console) ===		=== 50-pin Cartridge Bus (looking into console) ===
	{\| class="wikitable styled-table" style="width:95%; text-align:center; font-size:90%;"		{\| class="wikitable styled-table" style="width:95%; text-align:center; font-size:90%;"
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	\|}		\|}

	== 📜 Historical Context & Sales ==		== Historical Context & Sales ==
	* '''1985''' – Sega launches the ''Mark III'' in Japan; hardware overhaul of the SG-1000 line.		* '''1985''' – Sega launches the ''Mark III'' in Japan; hardware overhaul of the SG-1000 line.
	* '''1986''' – Re-packaged for North America as the '''“Sega System”''', quickly re-branded '''Master System''' under Tonka; bundled with ''Hang-On/Safari Hunt'' combo cartridge.		* '''1986''' – Re-packaged for North America as the '''“Sega System”''', quickly re-branded '''Master System''' under Tonka; bundled with ''Hang-On/Safari Hunt'' combo cartridge.
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	Global lifetime sales are estimated at '''≈ 13 million''' (vs ~62 M NES).		Global lifetime sales are estimated at '''≈ 13 million''' (vs ~62 M NES).

	== 🔧 Maintenance & Common Faults ==		== Maintenance & Common Faults ==
	* Cracked solder on AV DIN → intermittent video.		* Cracked solder on AV DIN → intermittent video.
	* 7805 regulator runs hot (VA2 boards) – recap & replace thermal pad.		* 7805 regulator runs hot (VA2 boards) – recap & replace thermal pad.
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	Detailed procedures: see '''[[Sega Master System General Maintenance]]''', '''[[Sega Master System Troubleshooting Guide]]''', '''[[Sega Master System Capacitor Replacement Guide]]''' and '''[[Sega Master System AV Output Modifications]]'''.		Detailed procedures: see '''[[Sega Master System General Maintenance]]''', '''[[Sega Master System Troubleshooting Guide]]''', '''[[Sega Master System Capacitor Replacement Guide]]''' and '''[[Sega Master System AV Output Modifications]]'''.

	== 🔄 Board Revisions & Known Errata ==		== Board Revisions & Known Errata ==
	{\| class="wikitable styled-table" style="width:90%; text-align:center;"		{\| class="wikitable styled-table" style="width:90%; text-align:center;"
	! Rev !! Region (year) !! Notes / quirks		! Rev !! Region (year) !! Notes / quirks
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	\|}		\|}

	== 🎲 Game Media ==		== Game Media ==
	* '''ROM Cartridges''' up to 512 KB; larger titles employ paging ASICS (315-5208, 315-5235).		* '''ROM Cartridges''' up to 512 KB; larger titles employ paging ASICS (315-5208, 315-5235).
	* '''Sega Card''' thin 35 g card, limited to 32 KB/256 Kbit – discontinued 1989.		* '''Sega Card''' thin 35 g card, limited to 32 KB/256 Kbit – discontinued 1989.
	* FM soundtrack detected via mapper bit 6; Western carts often contain unused FM data later unlocked by community patches.		* FM soundtrack detected via mapper bit 6; Western carts often contain unused FM data later unlocked by community patches.

	== 🎯 Trivia & Pop-Culture ==		== Trivia & Pop-Culture ==
	* Hidden '''“Snail Maze”''' game embedded in BIOS v1.3 – launch by holding ↑ + 1 + 2 at the Sega logo.		* Hidden '''“Snail Maze”''' game embedded in BIOS v1.3 – launch by holding ↑ + 1 + 2 at the Sega logo.
	* Original Japanese unit’s 3-D glasses used active shutter synced via the /NMI pin; later re-used on Mega Drive add-ons.		* Original Japanese unit’s 3-D glasses used active shutter synced via the /NMI pin; later re-used on Mega Drive add-ons.
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	* Tec Toy released Brazilian-exclusive ports: ''Street Fighter II'', ''Mônica no Castelo do Dragão'' (Wonder Boy II reskin), sustaining the platform into the late 1990s.		* Tec Toy released Brazilian-exclusive ports: ''Street Fighter II'', ''Mônica no Castelo do Dragão'' (Wonder Boy II reskin), sustaining the platform into the late 1990s.

	== 📚 Further Reading ==		== Further Reading ==
	* ''[[Sega Master System Service Manual (1986)]]'' – Part #420-5718-01		* ''[[Sega Master System Service Manual (1986)]]'' – Part #420-5718-01
	* Chris Covell, “SMS VDP documentation & palette research” (covell.ski)		* Chris Covell, “SMS VDP documentation & palette research” (covell.ski)

Josh: /* 📚 Further Reading */

2025-04-27T09:20:09Z

📚 Further Reading

← Older revision		Revision as of 10:20, 27 April 2025
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	== 📚 Further Reading ==		== 📚 Further Reading ==
	* ''Sega Master System Service Manual (1986)'' – Part #420-5718-01		* ''[[Sega Master System Service Manual (1986)]]'' – Part #420-5718-01
	* Chris Covell, “SMS VDP documentation & palette research” (covell.ski)		* Chris Covell, “SMS VDP documentation & palette research” (covell.ski)
	* Charles MacDonald, “Master System Hardware Notes” (github.com/CharlesMacDonald)		* Charles MacDonald, “Master System Hardware Notes” (github.com/CharlesMacDonald)

	[[Category:Sega Systems]]		[[Category:Sega Systems]]

Josh: /* 🔧 Maintenance & Common Faults */

2025-04-27T09:17:26Z

🔧 Maintenance & Common Faults

← Older revision		Revision as of 10:17, 27 April 2025
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	* 7805 regulator runs hot (VA2 boards) – recap & replace thermal pad.		* 7805 regulator runs hot (VA2 boards) – recap & replace thermal pad.
	* Dying 315-5216 I/O ASIC causes random controller dropouts.		* Dying 315-5216 I/O ASIC causes random controller dropouts.
			[[File:Sega Master System (Model 1) PCB.png\|none\|thumb\|601x601px\|Sega Master System (Model 1) PCB]]
	Detailed procedures: see '''[[Sega Master System General Maintenance]]''', '''[[Sega Master System Troubleshooting Guide]]''', '''[[Sega Master System Capacitor Replacement Guide]]''' and '''[[Sega Master System AV Output Modifications]]'''.		Detailed procedures: see '''[[Sega Master System General Maintenance]]''', '''[[Sega Master System Troubleshooting Guide]]''', '''[[Sega Master System Capacitor Replacement Guide]]''' and '''[[Sega Master System AV Output Modifications]]'''.

Josh: /* 50-pin Cartridge Bus (looking into console) */

2025-04-27T09:15:49Z

50-pin Cartridge Bus (looking into console)

← Older revision		Revision as of 10:15, 27 April 2025
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	! Pin !! Signal !! Description !! Pin !! Signal !! Description		! Pin !! Signal !! Description !! Pin !! Signal !! Description
	\|-		\|-
	\| 1 \|~~\| {{small~~\|GND}} \|\| Ground \|\| 26 \|\| A11 \|\| Address 11		\| 1 \|\| GND \|\| Ground \|\| 26 \|\| A11 \|\| Address 11
	\|-		\|-
	\| 2 \|\| +5 V \|\| +5 V DC \|\| 27 \|\| A9 \|\| Address 9		\| 2 \|\| +5 V \|\| +5 V DC \|\| 27 \|\| A9 \|\| Address 9

Josh at 09:09, 27 April 2025

2025-04-27T09:09:38Z

← Older revision		Revision as of 10:09, 27 April 2025
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	\| os = None (8 KB BIOS v1.3 – menu + hidden Snail Maze)		\| os = None (8 KB BIOS v1.3 – menu + hidden Snail Maze)
	\| predecessor = [[Sega SG-1000 II]]		\| predecessor = [[Sega SG-1000 II]]
	\| successor = [[Sega ~~Mega Drive~~]]		\| successor = [[Sega Master System II]]
	\| codename = ''Mark III''		\| codename = ''Mark III''
	\| model = MK-2000 / MK-3000		\| model = MK-2000 / MK-3000

Josh at 09:09, 27 April 2025

2025-04-27T09:09:07Z

← Older revision		Revision as of 10:09, 27 April 2025
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	{{Infobox computer		{{Infobox computer
	\| name = Sega Master System (Model 1)		\| name = Sega Master System (Model 1)
	\| image = [[File:Sega-Master-System-~~MK-2000~~.jpg\|260px\|frameless]]		\| image = [[File:Sega-Master-System-Set.jpg\|260px\|frameless]]
	\| caption = First-generation «Master System» console (MK-2000, 1986) with cartridge & Sega Card slots		\| caption = First-generation «Master System» console (MK-2000, 1986) with cartridge & Sega Card slots
	\| manufacturer = Sega Enterprises, Ltd.		\| manufacturer = Sega Enterprises, Ltd.

Josh: /* Exact 64 KB CPU Memory-Map (Model 1) */

2025-04-27T09:08:13Z

Exact 64 KB CPU Memory-Map (Model 1)

← Older revision		Revision as of 10:08, 27 April 2025
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	=== Exact 64 KB CPU Memory-Map (Model 1) ===		=== Exact 64 KB CPU Memory-Map (Model 1) ===
	{\| class="wikitable styled-table" style="width:80%; text-align:center;"		{\| class="wikitable styled-table" style="width:70%; text-align:center;"
	\|+''Z80 Address Space''		\|+''Z80 Address Space''
	! Range !! Size !! Purpose / Notes		! Range !! Size !! Purpose / Notes
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	\|}		\|}

	Mapper registers are written through bogus addresses $FFFC–$FFFF (upper bits decoded by on-cart ASICs such as 315-5196).		''Mapper registers'' are written through bogus addresses $FFFC–$FFFF (upper bits decoded by on-cart ASICs such as 315-5196).

	=== BIOS Entry Points (v1.3) ===		=== BIOS Entry Points (v1.3) ===

Josh: /* 🧠 System Architecture */

2025-04-27T09:07:48Z

🧠 System Architecture

← Older revision		Revision as of 10:07, 27 April 2025
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	== 🧠 System Architecture ==		== 🧠 System Architecture ==
	{\| class="wikitable styled-table" style="width:90%; text-align:center;"		{\| class="wikitable styled-table" style="width:70%; text-align:center;"
	! Sub-system !! Specification (Master System Model 1)		! Sub-system !! Specification (Master System Model 1)
	\|-		\|-

Josh: Created page with "{{Infobox computer | name = Sega Master System (Model 1) | image = frameless | caption = First-generation «Master System» console (MK-2000, 1986) with cartridge & Sega Card slots | manufacturer = Sega Enterprises, Ltd. | type = Home video-game console | release date = {{Plainlist| * JP (as '''Sega Mark III''') – '''20 Oct 1985''' * NA – '''Jun 1986''' * EU / Oceania – '''Sep..."

2025-04-27T09:07:33Z

Created page with "{{Infobox computer | name = Sega Master System (Model 1) | image = 260px|frameless | caption = First-generation «Master System» console (MK-2000, 1986) with cartridge & Sega Card slots | manufacturer = Sega Enterprises, Ltd. | type = Home video-game console | release date = {{Plainlist| * JP (as '''Sega Mark III''') – '''20 Oct 1985''' * NA – '''Jun 1986''' * EU / Oceania – '''Sep..."

New page

{{Infobox computer
| name = Sega Master System (Model 1)
| image = [[File:Sega-Master-System-MK-2000.jpg|260px|frameless]]
| caption = First-generation «Master System» console (MK-2000, 1986) with cartridge & Sega Card slots
| manufacturer = Sega Enterprises, Ltd.
| type = Home video-game console
| release date = {{Plainlist|
* JP (as '''Sega Mark III''') – '''20 Oct 1985'''
* NA – '''Jun 1986'''
* EU / Oceania – '''Sep 1987'''
}}
| discontinued = {{Plainlist|
* JP – 1989 (replaced by Master System [JP])
* NA – 1991
* EU – 1996 (budget rerelease by Majesco)
}}
| price = US$199 (NA launch bundle, 1986)
| cpu = Zilog Z80A @ '''3 579 545 Hz''' (NTSC) / '''3 546 895 Hz''' (PAL)
| memory = 8 KB work-RAM • 16 KB video-RAM
| storage = ROM cartridges (max 4 Mbit) • Sega Card (256 Kbit) • optional FM sound BIOS (Japan)
| display = VDP 315-5124/5246 → 256 × 192 (nom.) / 32-colour on-screen from 64-colour palette
| sound = SN76489-compatible PSG (3 square + 1 noise) • optional '''YM2413 FM''' add-on (JP)
| dimensions = 365 mm W × 170 mm D × 66 mm H
| weight = ≈ 2.1 kg
| os = None (8 KB BIOS v1.3 – menu + hidden Snail Maze)
| predecessor = [[Sega SG-1000 II]]
| successor = [[Sega Mega Drive]]
| codename = ''Mark III''
| model = MK-2000 / MK-3000
}}

The '''Sega Master System''' (first-generation “Model 1”, product code '''MK-2000''') is an 8-bit home console released by Sega to compete directly with Nintendo’s Famicom/NES. Re-branded from the Japan-only '''Sega Mark III''', the Master System introduced the distinctive black-and-red industrial design, a combo cartridge + “[[Sega Card]]” slot, and an edge expansion port supporting FM audio, 3-D glasses and future accessories. Although outsold by Nintendo in Japan & North America, it enjoyed major success across Europe, Brazil and Australasia, shipping an estimated '''≈ 13 million units''' worldwide.

== 🧠 System Architecture ==
{| class="wikitable styled-table" style="width:90%; text-align:center;"
! Sub-system !! Specification (Master System Model 1)
|-
| '''CPU''' || Z80A 8-bit @ 3.58 MHz (NTSC) / 3.55 MHz (PAL) • 16-bit address – 64 KB space
|-
| '''VDP''' || Sega 315-5124 (NTSC) / 315-5246 (PAL)
TMS9918-derived: 2× pattern tables, 32 sprites (8 per scan-line)
VRAM 16 KB (dual 8 KB SRAM, 5 ns page registers)
|-
| '''Palette''' || 64 colours (6-bit RGB) – 32 on-screen (background & sprite)
|-
| '''Audio''' || TI SN76489 PSG (integrated into VDP) – 3 square + 1 noise
Expansion pin-out for YM2413 FM (used in JP “FM Unit” & Mark III)
|-
| '''Main RAM''' || 2 × 8 KB HM6264 (work-RAM) @ ~150 ns
|-
| '''Cartridge ROM''' || Up to 4 Mbit/512 KB (LoROM/HiROM mapper chips: Sega 315-5235, 315-5208, etc.)
|-
| '''BIOS''' || 8 KB mask ROM ver 1.3 (NA/EU) — intro menu + hidden Snail Maze (hold ↑+1+2)
|-
| '''I/O''' || 2× DE-9 game-pad, RF-UHF & 8-pin AV, Card slot (36-pin), 50-pin cart, 35-pin EXT
|}

=== Exact 64 KB CPU Memory-Map (Model 1) ===
{| class="wikitable styled-table" style="width:80%; text-align:center;"
|+''Z80 Address Space''
! Range !! Size !! Purpose / Notes
|-
| $0000 – $3FFF || 16 KB || '''ROM–0''' (Cartridge / Card / BIOS)
|-
| $4000 – $7FFF || 16 KB || '''ROM–1''' (bank-selectable via mapper)
|-
| $8000 – $BFFF || 16 KB || '''ROM–2''' (bank-selectable)
|-
| $C000 – $DFFF || 8 KB || '''Work-RAM''' (on-board)
|-
| $E000 – $FFFF || 8 KB || Mirror of $C000 – $DFFF
|}

*Mapper registers* are written through bogus addresses $FFFC–$FFFF (upper bits decoded by on-cart ASICs such as 315-5196).

=== BIOS Entry Points (v1.3) ===
{| class="wikitable styled-table" style="width:70%; text-align:center;"
! Address !! Routine
|-
| $0000 || Soft reset → Sega splash & checksum
|-
| $00A8 || PSG mute / init
|-
| $0150 || Card detect loop
|-
| $0200 || Hidden game “Snail Maze” (activate ↑+1+2 at logo)
|}

== 📺 Video Timing ==
{| class="wikitable styled-table" style="width:70%; text-align:center;"
! Parameter !! NTSC !! PAL
|-
| Master clock || 10.738635 MHz || 10.644606 MHz
|-
| Pixel clock || 5.369 MHz || 5.322 MHz
|-
| Lines/frame || 262 || 313
|-
| Refresh || 59.92 Hz || 49.70 Hz
|}

== 🔌 Edge-Connector Pin-out ==
=== 50-pin Cartridge Bus (looking into console) ===
{| class="wikitable styled-table" style="width:95%; text-align:center; font-size:90%;"
! Pin !! Signal !! Description !! Pin !! Signal !! Description
|-
| 1 || {{small|GND}} || Ground || 26 || A11 || Address 11
|-
| 2 || +5 V || +5 V DC || 27 || A9 || Address 9
|-
| 3 || CLOCK || M-clock (5.37 MHz) || 28 || A8
|-
| 4 || A15 || Address 15 || 29 || A13
|-
| 5 || A14 || Address 14 || 30 || A7
|-
| 6 || A12 || Address 12 || 31 || A6
|-
| 7 || /MREQ || Z80 Memory Request || 32 || A5
|-
| 8 || /IORQ || I/O Request || 33 || A4
|-
| 9 || /RD || Read strobe || 34 || A3
|-
| 10 || /WR || Write strobe || 35 || A2
|-
| 11 || D7 || Data 7 || 36 || A1
|-
| 12 || D6 || Data 6 || 37 || A0
|-
| 13 || D5 || Data 5 || 38 || CE ''(low)''
|-
| 14 || D4 || Data 4 || 39 || +5 V
|-
| 15 || D3 || Data 3 || 40 || /BUSREQ (rarely used)
|-
| 16 || D2 || Data 2 || 41 || PAUSE (pulled-up: cartridge can assert)
|-
| 17 || D1 || Data 1 || 42 || /RESET
|-
| 18 || D0 || Data 0 || 43 || AUDIO IN (FM/stereo mods)
|-
| 19 || M1 || Op-code fetch || 44 || /NMI (3-D glasses)
|-
| 20 || RFSH || Refresh || 45 || GND
|-
| 21 || /HALT || CPU halt || 46 || GND
|-
| 22 || A10 || Address 10 || 47 || +5 V
|-
| 23 || '''-''' || (n/c) || 48 || +5 V (cart power)
|-
| 24 || '''-''' || (n/c) || 49 || '''-'''
|-
| 25 || A16 || Address 16 (mapper) || 50 || '''-'''
|}

== 📜 Historical Context & Sales ==
* '''1985''' – Sega launches the ''Mark III'' in Japan; hardware overhaul of the SG-1000 line.
* '''1986''' – Re-packaged for North America as the '''“Sega System”''', quickly re-branded '''Master System''' under Tonka; bundled with ''Hang-On/Safari Hunt'' combo cartridge.
* '''1987–1992''' – Becomes the dominant 8-bit console across Europe, distributed by Virgin Mastertronic; library balloons to 300+ PAL titles.
* '''Brazil''' – Tec Toy begins local production (1989) and continues updated revisions into the 2020s; > 8 million units sold in Brazil alone.
Global lifetime sales are estimated at '''≈ 13 million''' (vs ~62 M NES).

== 🔧 Maintenance & Common Faults ==
* Cracked solder on AV DIN → intermittent video.
* 7805 regulator runs hot (VA2 boards) – recap & replace thermal pad.
* Dying 315-5216 I/O ASIC causes random controller dropouts.
Detailed procedures: see '''[[Sega Master System General Maintenance]]''', '''[[Sega Master System Troubleshooting Guide]]''', '''[[Sega Master System Capacitor Replacement Guide]]''' and '''[[Sega Master System AV Output Modifications]]'''.

== 🔄 Board Revisions & Known Errata ==
{| class="wikitable styled-table" style="width:90%; text-align:center;"
! Rev !! Region (year) !! Notes / quirks
|-
| VA0 || JP (1985) || Mark III PCB – discrete VDP/PSG, no BIOS, external FM Unit
|-
| VA2 || NA/EU (1986) || First “Master System” – large RF can, 8 KB BIOS v1.3, 5 × 5 V regulators; early units prone to jail-bar video (unscreened VRAM lines)
|-
| VA3 || EU (1987) || Card slot EMI shield deleted, improved RF modulator
|-
| VA5 || EU (1989) || 315-5246 PAL VDP, YM2413 traces removed; RGB DIN 8 output added
|-
| VA6 || BR (1991) || Tec Toy – onboard TMSS lockout stub, composite only (no RF)
|}

== 🎲 Game Media ==
* '''ROM Cartridges''' up to 512 KB; larger titles employ paging ASICS (315-5208, 315-5235).
* '''Sega Card''' thin 35 g card, limited to 32 KB/256 Kbit – discontinued 1989.
* FM soundtrack detected via mapper bit 6; Western carts often contain unused FM data later unlocked by community patches.

== 🎯 Trivia & Pop-Culture ==
* Hidden '''“Snail Maze”''' game embedded in BIOS v1.3 – launch by holding ↑ + 1 + 2 at the Sega logo.
* Original Japanese unit’s 3-D glasses used active shutter synced via the /NMI pin; later re-used on Mega Drive add-ons.
* The console appears in '''Charlie Brooker’s _Black Mirror_''' episode “Bandersnatch” (retro game-dev setting).
* Tec Toy released Brazilian-exclusive ports: ''Street Fighter II'', ''Mônica no Castelo do Dragão'' (Wonder Boy II reskin), sustaining the platform into the late 1990s.

== 📚 Further Reading ==
* ''Sega Master System Service Manual (1986)'' – Part #420-5718-01
* Chris Covell, “SMS VDP documentation & palette research” (covell.ski)
* Charles MacDonald, “Master System Hardware Notes” (github.com/CharlesMacDonald)

[[Category:Sega Systems]]