Sega CD (Model 1) - Revision history

Josh: Undo revision 3806 by Josh (talk)

2025-05-12T09:10:22Z

Undo revision 3806 by Josh (talk)

Josh at 09:10, 12 May 2025

2025-05-12T09:10:06Z

Josh at 09:10, 12 May 2025

2025-05-12T09:10:01Z

Josh: /* 🧰 General maintenance */

2025-05-09T16:13:25Z

🧰 General maintenance

← Older revision		Revision as of 17:13, 9 May 2025
Line 141:		Line 141:

	== 🧰 General maintenance ==		== 🧰 General maintenance ==
	Full disassembly, recap lists and belt change procedure: see [[Sega CD (Model 1) ~~General~~ Maintenance Guide]].		Full disassembly, recap lists and belt change procedure: see [[Sega CD (Model 1) Maintenance Guide]].
	Capacitor map and polarity silks are on [[Sega CD (Model 1) Capacitor Replacement Guide]].		Capacitor map and polarity silks are on [[Sega CD (Model 1) Capacitor Replacement Guide]].

Josh at 11:17, 27 April 2025

2025-04-27T11:17:59Z

← Older revision		Revision as of 12:17, 27 April 2025
Line 5:		Line 5:
	\| manufacturer = Sega Enterprises Ltd.<br />Optical block by [[Sony]] (KSS-240A/KSS-240R)		\| manufacturer = Sega Enterprises Ltd.<br />Optical block by [[Sony]] (KSS-240A/KSS-240R)
	\| type = CD-ROM add-on console		\| type = CD-ROM add-on console
	\| release date = {{Start date\|1991\|12\|12}} (JP Mega-CD)<br />{{Start date\|1992\|10\|15}} (US Sega CD)<br />{{Start date\|1993\|05\|01}} (EU Mega-CD)		\| release date = {{Start date\|1991\|12\|12}} (JP Mega-CD)<br />{{Start date\|1992\|10\|15}} (US Sega CD)<br />{{Start date\|1993\|05\|01}} (EU Mega-CD)
	\| discontinued = 1994 (superseded by Side-loader & Model 2)		\| discontinued = 1994 (superseded by Side-loader & Model 2)
	\| price = JP ¥49 800 • US US$299 • EU £270		\| price = JP ¥49 800 • US US$299 • EU £270

Josh at 11:14, 27 April 2025

2025-04-27T11:14:32Z

← Older revision		Revision as of 12:14, 27 April 2025
Line 5:		Line 5:
	\| manufacturer = Sega Enterprises Ltd.<br />Optical block by [[Sony]] (KSS-240A/KSS-240R)		\| manufacturer = Sega Enterprises Ltd.<br />Optical block by [[Sony]] (KSS-240A/KSS-240R)
	\| type = CD-ROM add-on console		\| type = CD-ROM add-on console
	\| release date = \|-{{Start date\|1991\|12\|12}} (JP Mega-CD)<br />{{Start date\|1992\|10\|15}} (US Sega CD)<br />{{Start date\|1993\|05\|01}} (EU Mega-CD)		\| release date = {{Start date\|1991\|12\|12}} (JP Mega-CD)<br />{{Start date\|1992\|10\|15}} (US Sega CD)<br />{{Start date\|1993\|05\|01}} (EU Mega-CD)
	\| discontinued = 1994 (superseded by Side-loader & Model 2)		\| discontinued = 1994 (superseded by Side-loader & Model 2)
	\| price = JP ¥49 800 • US US$299 • EU £270		\| price = JP ¥49 800 • US US$299 • EU £270

Josh at 11:14, 27 April 2025

2025-04-27T11:14:04Z

← Older revision		Revision as of 12:14, 27 April 2025
Line 5:		Line 5:
	\| manufacturer = Sega Enterprises Ltd.<br />Optical block by [[Sony]] (KSS-240A/KSS-240R)		\| manufacturer = Sega Enterprises Ltd.<br />Optical block by [[Sony]] (KSS-240A/KSS-240R)
	\| type = CD-ROM add-on console		\| type = CD-ROM add-on console
	\| release date = {{Start date\|1991\|12\|12}} JP Mega-CD <br /> {{Start date\|1992\|10\|15}} US Sega CD <br /> {{Start date\|1993\|05}} EU Mega-CD		\| release date = \|-{{Start date\|1991\|12\|12}} (JP Mega-CD)<br />{{Start date\|1992\|10\|15}} (US Sega CD)<br />{{Start date\|1993\|05\|01}} (EU Mega-CD)
	\| discontinued = 1994 (superseded by Side-loader & Model 2)		\| discontinued = 1994 (superseded by Side-loader & Model 2)
	\| price = JP ¥49 800 • US US$299 • EU £270		\| price = JP ¥49 800 • US US$299 • EU £270

Josh: /* 🔌 Pin-by-pin expansion bus */

2025-04-27T11:13:07Z

🔌 Pin-by-pin expansion bus

← Older revision		Revision as of 12:13, 27 April 2025
Line 113:		Line 113:
	\| B49 \|\| – \|\| +5 V \|\|		\| B49 \|\| – \|\| +5 V \|\|
	\|-		\|-
	\| B50 \| – \| GND \|		\| B50 \|\| – \|\| GND \|\|
	\|}		\|}

Josh: /* 🔌 Pin-by-pin expansion bus */

2025-04-27T11:12:43Z

🔌 Pin-by-pin expansion bus

← Older revision		Revision as of 12:12, 27 April 2025
Line 92:		Line 92:
	The 50-pin edge (CN-B) carries the Genesis 68000 bus plus additional DMA and audio lines:		The 50-pin edge (CN-B) carries the Genesis 68000 bus plus additional DMA and audio lines:

	{\| class="wikitable styled-table" style="width:~~100~~%;"		{\| class="wikitable styled-table" style="width:70%;"
	! Pin !! Dir !! Name !! Description		! Pin !! Dir !! Name !! Description
	\|-		\|-

Josh at 11:09, 27 April 2025

2025-04-27T11:09:14Z

← Older revision		Revision as of 12:09, 27 April 2025
Line 5:		Line 5:
	\| manufacturer = Sega Enterprises Ltd.<br />Optical block by [[Sony]] (KSS-240A/KSS-240R)		\| manufacturer = Sega Enterprises Ltd.<br />Optical block by [[Sony]] (KSS-240A/KSS-240R)
	\| type = CD-ROM add-on console		\| type = CD-ROM add-on console
	\| release date = {{Start date\|1991\|12\|12}} JP Mega-CD<br />{{Start date\|1992\|10\|15}} US Sega CD<br />{{Start date\|1993\|05}} EU Mega-CD		\| release date = {{Start date\|1991\|12\|12}} JP Mega-CD <br /> {{Start date\|1992\|10\|15}} US Sega CD <br /> {{Start date\|1993\|05}} EU Mega-CD
	\| discontinued = 1994 (superseded by Side-loader & Model 2)		\| discontinued = 1994 (superseded by Side-loader & Model 2)
	\| price = JP ¥49 800 • US US$299 • EU £270		\| price = JP ¥49 800 • US US$299 • EU £270

← Older revision		Revision as of 10:10, 12 May 2025
Line 29:		Line 29:
	Released in late 1991, it augmented the base console with a faster 12.5 MHz 68EC000, hardware scaling/rotation ASICs, 8-channel PCM audio and the ability to stream full-motion video (Cinepak) from CD-ROM.		Released in late 1991, it augmented the base console with a faster 12.5 MHz 68EC000, hardware scaling/rotation ASICs, 8-channel PCM audio and the ability to stream full-motion video (Cinepak) from CD-ROM.

	== 🕰️ Historical context & sales ==		== Historical context & sales ==
	* '''Concept (1989–1990):''' Sega R&D2 (Hisashi Suzuki) partnered with Sony Devices Div. to adopt the KSS-240 laser deck.		* '''Concept (1989–1990):''' Sega R&D2 (Hisashi Suzuki) partnered with Sony Devices Div. to adopt the KSS-240 laser deck.
	* '''Launch:''' 12 Dec 1991, JP ¥49 800 – initial shipment 100 k; supply shortages until Feb 1992.		* '''Launch:''' 12 Dec 1991, JP ¥49 800 – initial shipment 100 k; supply shortages until Feb 1992.
Line 35:		Line 35:
	* '''Total Model 1 units:''' ≈ 600 k worldwide (of 2.2 M total Sega CD family).		* '''Total Model 1 units:''' ≈ 600 k worldwide (of 2.2 M total Sega CD family).

	== 🧠 Architecture overview ==		== Architecture overview ==
	{\| class="wikitable styled-table" style="width:70%; text-align:center;"		{\| class="wikitable styled-table" style="width:70%; text-align:center;"
	! Sub-system !! IC(s) !! Notes		! Sub-system !! IC(s) !! Notes
Line 54:		Line 54:
	\|}		\|}

	== 📊 Technical specification (Model 1, BIOS v1.10) ==		== Technical specification (Model 1, BIOS v1.10) ==
	{\| class="wikitable styled-table" style="width:70%; text-align:center;"		{\| class="wikitable styled-table" style="width:70%; text-align:center;"
	\|-		\|-
	! ~~colspan="2"~~ style="background:#ddd;"\|Processing		! style="background:#ddd;" \|Processing
	\|-		\|-
	\| Main 68k \| 12.500 MHz (25 MHz ÷ 2) wait-stated 3–4 cycles to word-RAM		\| Main 68k \| 12.500 MHz (25 MHz ÷ 2) wait-stated 3–4 cycles to word-RAM
Line 65:		Line 65:
	\| DMA \| 5.0 MB·s⁻¹ peak host⇄word-RAM		\| DMA \| 5.0 MB·s⁻¹ peak host⇄word-RAM
	\|-		\|-
	! ~~colspan="2"~~ style="background:#ddd;"\|Memory map (simplified)		! style="background:#ddd;" \|Memory map (simplified)
	\|-		\|-
	\| $0000 00–$1F FFFF \| 2 MB Program RAM		\| $0000 00–$1F FFFF \| 2 MB Program RAM
Line 89:		Line 89:
	* V-blank interrupt every 262 lines NTSC (≈ 59.92 Hz).		* V-blank interrupt every 262 lines NTSC (≈ 59.92 Hz).

	== 🔌 Pin-by-pin expansion bus ==		== Pin-by-pin expansion bus ==
	The 50-pin edge (CN-B) carries the Genesis 68000 bus plus additional DMA and audio lines:		The 50-pin edge (CN-B) carries the Genesis 68000 bus plus additional DMA and audio lines:

Line 118:		Line 118:
	Full table with all 50 pins on [[Mega Drive expansion port pinout]].		Full table with all 50 pins on [[Mega Drive expansion port pinout]].

	== 🛠️ Known hardware revisions & PCB errata ==		== Known hardware revisions & PCB errata ==
	{\| class="wikitable styled-table" style="width:90%; text-align:center;"		{\| class="wikitable styled-table" style="width:90%; text-align:center;"
	! Assy # !! Board silk !! Region !! Notable changes / bugs !! Service fixes		! Assy # !! Board silk !! Region !! Notable changes / bugs !! Service fixes
Line 125:		Line 125:
	\|-		\|-
	\| 171-5978B \|\| VA1 \|\| US \| BIOS 1.10, word-RAM wait fix \|\| Add R511 pull-up (factory bodge)		\| 171-5978B \|\| VA1 \|\| US \| BIOS 1.10, word-RAM wait fix \|\| Add R511 pull-up (factory bodge)
			\|
	\|-		\|-
	\| 171-5978C \|\| VA2 \|\| EU \| CXD1162 rev-C, 315-5548A ASIC \|\| 74HC00 (IC15) ESD prone – replace with HCT		\| 171-5978C \|\| VA2 \|\| EU \| CXD1162 rev-C, 315-5548A ASIC \|\| 74HC00 (IC15) ESD prone – replace with HCT
			\|
	\|}		\|}

	== 🔧 Common failure points ==		== Common failure points ==
	* '''“GREEN LED but no spin”''' – blown surface-mount fuse F301 (2 A) or shorted 5 V tantalum C230.		* '''“GREEN LED but no spin”''' – blown surface-mount fuse F301 (2 A) or shorted 5 V tantalum C230.
	* '''Tray won’t eject / belt slip''' – 40 mm × 1.2 mm neoprene belt hardened. Replace with 41 mm 0.6 mm square belt.		* '''Tray won’t eject / belt slip''' – 40 mm × 1.2 mm neoprene belt hardened. Replace with 41 mm 0.6 mm square belt.
Line 137:		Line 139:
	* '''Backup RAM corrupt''' – CR2032 coin cell dead or IC3 SRM2016 failing.		* '''Backup RAM corrupt''' – CR2032 coin cell dead or IC3 SRM2016 failing.

	== 🔩 Service manuals & schematics ==		== Service manuals & schematics ==
	* [[Sega CD Service Manual\|Sega Service Document #170-0436-01]]		* [[Sega CD Service Manual\|Sega Service Document #170-0436-01]]

	== 🧰 General maintenance ==		== General maintenance ==
	Full disassembly, recap lists and belt change procedure: see [[Sega CD (Model 1) Maintenance Guide]].		Full disassembly, recap lists and belt change procedure: see [[Sega CD (Model 1) Maintenance Guide]].
	Capacitor map and polarity silks are on [[Sega CD (Model 1) Capacitor Replacement Guide]].		Capacitor map and polarity silks are on [[Sega CD (Model 1) Capacitor Replacement Guide]].

	== 🩺 Troubleshooting ==		== Troubleshooting ==
	A step-by-step power-on diagnostic flow (LED blink codes, fuse chart, clock probing) is available on [[Sega CD (Model 1) Troubleshooting Guide]].		A step-by-step power-on diagnostic flow (LED blink codes, fuse chart, clock probing) is available on [[Sega CD (Model 1) Troubleshooting Guide]].

	== 🔉 Audio/Video modifications ==		== Audio/Video modifications ==
	* Direct-mix “board-jail”: lift R171 &R172, route RF5C164 output to Genesis EXT stereo jack – no crosstalk.		* Direct-mix “board-jail”: lift R171 &R172, route RF5C164 output to Genesis EXT stereo jack – no crosstalk.
	* RGB bypass: use Genesis VDP RGB; Sega CD adds no extra graphics plane, so standard MD RGB mod applies.		* RGB bypass: use Genesis VDP RGB; Sega CD adds no extra graphics plane, so standard MD RGB mod applies.
	* 50/60 Hz region switch – tie ASIC pin 4 ‘AREA’ to DIP switch + patch BIOS byte $1FE1.		* 50/60 Hz region switch – tie ASIC pin 4 ‘AREA’ to DIP switch + patch BIOS byte $1FE1.

	== 📀 Software & homebrew ==		== Software & homebrew ==
	Model 1 BIOS 1.10 supports '''CD-R''' if session is MODE1+CDDA (avoid 40× burns). Recommended test suites: ‘’Sega CD Test Disc’’ by discedge; ‘’RAM Stress’’ by Luke Usher.		Model 1 BIOS 1.10 supports '''CD-R''' if session is MODE1+CDDA (avoid 40× burns). Recommended test suites: ‘’Sega CD Test Disc’’ by discedge; ‘’RAM Stress’’ by Luke Usher.

	== 🎲 Trivia & pop-culture ==		== Trivia & pop-culture ==
	* ‘’Snatcher’’ (JP) used SCD PCM channels for full Japanese voice acting – a first on 8 Mbit disc.		* ‘’Snatcher’’ (JP) used SCD PCM channels for full Japanese voice acting – a first on 8 Mbit disc.
	* The launch bundle ‘’Sol-Feace’’ shipped on both cart (JP) and CD; players compared load-times as marketing.		* The launch bundle ‘’Sol-Feace’’ shipped on both cart (JP) and CD; players compared load-times as marketing.