Sinclair ZX Spectrum - Revision history

ZXSpectrum128: Correct speed of tape loading on the ZX Spectrum is approximately 1500 baud, the wrong speed given on this wiki's website was 300 baud which is the speed a ZX81 will use for tape loading.

2026-04-23T08:12:26Z

Correct speed of tape loading on the ZX Spectrum is approximately 1500 baud, the wrong speed given on this wiki's website was 300 baud which is the speed a ZX81 will use for tape loading.

← Older revision		Revision as of 09:12, 23 April 2026
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	== Storage ==		== Storage ==
	Data is loaded and saved via a standard cassette tape interface operating at '''~~300~~ baud'''. The average loading time for a game is approximately 3-5 minutes, depending on the size of the program.		Data is loaded and saved via a standard cassette tape interface operating at approximately '''1500 baud'''. The average loading time for a game is approximately 3-5 minutes, depending on the size of the program.

	== I/O and Expansion ==		== I/O and Expansion ==

Josh at 09:37, 12 May 2025

2025-05-12T09:37:54Z

← Older revision		Revision as of 10:37, 12 May 2025
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	The '''Sinclair ZX Spectrum''' is an 8-bit home computer released by '''Sinclair Research Ltd''' in April 1982. It became a defining product of the early home computing era in the UK, known for its distinctive rubber keyboard and vibrant color graphics. The ZX Spectrum sold over 5 million units and is credited with popularizing home computing and gaming in the UK.		The '''Sinclair ZX Spectrum''' is an 8-bit home computer released by '''Sinclair Research Ltd''' in April 1982. It became a defining product of the early home computing era in the UK, known for its distinctive rubber keyboard and vibrant color graphics. The ZX Spectrum sold over 5 million units and is credited with popularizing home computing and gaming in the UK.

	== 🧠 Architecture ==		== Architecture ==
	* '''CPU''' – Zilog Z80A microprocessor clocked at '''3.5 MHz'''.		* '''CPU''' – Zilog Z80A microprocessor clocked at '''3.5 MHz'''.
	* '''ROM''' – 16 KB or 48 KB ROM containing Sinclair BASIC and system routines.		* '''ROM''' – 16 KB or 48 KB ROM containing Sinclair BASIC and system routines.
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	The ZX Spectrum generates video using a technique called "bit-banging," where the Z80 CPU directly controls the display output. The screen resolution is '''256×192 pixels''' with a palette of 15 colors, plus black. The unique attribute system allows for color attributes to be assigned to 8×8 pixel blocks, resulting in colorful graphics but also potential color clash.		The ZX Spectrum generates video using a technique called "bit-banging," where the Z80 CPU directly controls the display output. The screen resolution is '''256×192 pixels''' with a palette of 15 colors, plus black. The unique attribute system allows for color attributes to be assigned to 8×8 pixel blocks, resulting in colorful graphics but also potential color clash.

	== 💾 Storage ==		== Storage ==
	Data is loaded and saved via a standard cassette tape interface operating at '''300 baud'''. The average loading time for a game is approximately 3-5 minutes, depending on the size of the program.		Data is loaded and saved via a standard cassette tape interface operating at '''300 baud'''. The average loading time for a game is approximately 3-5 minutes, depending on the size of the program.

	== 🔌 I/O and Expansion ==		== I/O and Expansion ==
	* '''Edge connector (50-way)''' – provides access to the full Z80 bus, power, and video signals.		* '''Edge connector (50-way)''' – provides access to the full Z80 bus, power, and video signals.
	* '''9 V DC input''' – unregulated power supply.		* '''9 V DC input''' – unregulated power supply.
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	: ''ZX Printer, joystick interfaces, and various RAM expansion packs.''		: ''ZX Printer, joystick interfaces, and various RAM expansion packs.''

	== 🔧 Known PCB Revisions & Errata ==		== Known PCB Revisions & Errata ==
	{\| class="wikitable styled-table" style="width:70%; text-align:center;"		{\| class="wikitable styled-table" style="width:70%; text-align:center;"
	\|+'''ZX Spectrum PCB Revisions'''		\|+'''ZX Spectrum PCB Revisions'''
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	\|}		\|}

	== 🛠️ General Maintenance ==		== General Maintenance ==
	{\| class="wikitable styled-table" style="width:70%; text-align:center;"		{\| class="wikitable styled-table" style="width:70%; text-align:center;"
	! Issue !! Cause !! Remedy		! Issue !! Cause !! Remedy
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	Regular maintenance, including cleaning the keyboard and ensuring proper connections, can help prolong the life of the ZX Spectrum.		Regular maintenance, including cleaning the keyboard and ensuring proper connections, can help prolong the life of the ZX Spectrum.

	== 📜 Schematic & PCB ==		== Schematic & PCB ==
	The complete schematic for the ZX Spectrum is available for enthusiasts and repair technicians.		The complete schematic for the ZX Spectrum is available for enthusiasts and repair technicians.
	{\| class="wikitable"		{\| class="wikitable"
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	\|}		\|}

	== 🔧 Common Modifications ==		== Common Modifications ==
	* '''RAM upgrade''' – Adding external RAM packs to increase memory capacity.		* '''RAM upgrade''' – Adding external RAM packs to increase memory capacity.
	* '''Composite video mod''' – For improved video output quality on modern displays.		* '''Composite video mod''' – For improved video output quality on modern displays.
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	* '''Turbo mode modification''' – Overclocking the Z80 for faster performance (requires careful tuning).		* '''Turbo mode modification''' – Overclocking the Z80 for faster performance (requires careful tuning).

	== 🔢 ROM Keyword Map ==		== ROM Keyword Map ==
	Each key on the ZX Spectrum keyboard has multiple functions depending on the mode:		Each key on the ZX Spectrum keyboard has multiple functions depending on the mode:
	{\| class="wikitable styled-table" style="text-align:center;"		{\| class="wikitable styled-table" style="text-align:center;"
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	\|}		\|}

	== 🔗 Edge-Connector Pin-out ==		== Edge-Connector Pin-out ==
	<templatestyles src="Template:StyledTable/styles.css" />		<templatestyles src="Template:StyledTable/styles.css" />
	{\| class="wikitable styled-table" style="width:75%; text-align:center;"		{\| class="wikitable styled-table" style="width:75%; text-align:center;"

Josh at 13:23, 2 May 2025

2025-05-02T13:23:55Z

← Older revision		Revision as of 14:23, 2 May 2025
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	\| 8 \|\| '''A8''' \|\| \|\| 33 \|\| '''HALT'''		\| 8 \|\| '''A8''' \|\| \|\| 33 \|\| '''HALT'''
	\|}		\|}

			[[Category:Sinclair Computers]]

Josh: /* 🔗 Edge-Connector Pin-out */

2025-05-02T13:23:31Z

🔗 Edge-Connector Pin-out

← Older revision		Revision as of 14:23, 2 May 2025
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	\|-		\|-
	\| 2 \|\| '''A14''' \|\| \|\| 27 \|\| '''D5'''		\| 2 \|\| '''A14''' \|\| \|\| 27 \|\| '''D5'''
			\|
	\|-		\|-
	\| 3 \|\| '''A13''' \|\| \|\| 28 \|\| '''D6'''		\| 3 \|\| '''A13''' \|\| \|\| 28 \|\| '''D6'''
			\|
	\|-		\|-
	\| 4 \|\| '''A12''' \|\| \|\| 29 \|\| '''D7'''		\| 4 \|\| '''A12''' \|\| \|\| 29 \|\| '''D7'''
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	\|-		\|-
	\| 8 \|\| '''A8''' \|\| \|\| 33 \|\| '''HALT'''		\| 8 \|\| '''A8''' \|\| \|\| 33 \|\| '''HALT'''
	\|-		\|}
	~~\| 9 \|\|~~

Josh at 13:19, 2 May 2025

2025-05-02T13:19:12Z

← Older revision		Revision as of 14:19, 2 May 2025
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	\| codename = ZX Spectrum		\| codename = ZX Spectrum
	\| model = ZX Spectrum, ZX Spectrum+		\| model = ZX Spectrum, ZX Spectrum+
	\| logo = [[File:~~ZX_Spectrum_Logo~~.svg\|250px]]		\| logo = [[File:Sinclair ZX Spectrum-02b.svg\|250px]]
	}}		}}

Josh: Automated update by bot

2025-05-02T13:16:45Z

Automated update by bot

New page

{{Infobox computer
| name = Sinclair ZX Spectrum
| image = [[File:ZX_Spectrum.jpg|250px]]
| caption = Sinclair ZX Spectrum – The Iconic Home Computer
| manufacturer = Sinclair Research Ltd
| type = Home computer
| release date = April 1982
| discontinued = 1992
| price = £125 (1982)
| cpu = Zilog Z80A @ 3.5 MHz
| memory = 16 KB, 48 KB, or 128 KB RAM (varies by model)
| storage = External cassette tape (300 baud, EAR/MIC jacks)
| display = 256×192 pixels, 32 characters × 24 lines
| sound = Beeper (monophonic)
| dimensions = 23 cm × 14 cm × 4 cm (9.1" × 5.5" × 1.6")
| weight = 1.1 kg (2.4 lb)
| os = Sinclair BASIC in ROM
| predecessor = [[Sinclair ZX81]]
| successor = [[Sinclair ZX Spectrum+]]
| codename = ZX Spectrum
| model = ZX Spectrum, ZX Spectrum+
| logo = [[File:ZX_Spectrum_Logo.svg|250px]]
}}

The '''Sinclair ZX Spectrum''' is an 8-bit home computer released by '''Sinclair Research Ltd''' in April 1982. It became a defining product of the early home computing era in the UK, known for its distinctive rubber keyboard and vibrant color graphics. The ZX Spectrum sold over 5 million units and is credited with popularizing home computing and gaming in the UK.

== 🧠 Architecture ==
* '''CPU''' – Zilog Z80A microprocessor clocked at '''3.5 MHz'''.
* '''ROM''' – 16 KB or 48 KB ROM containing Sinclair BASIC and system routines.
* '''RAM''' – Available in 16 KB, 48 KB, or 128 KB configurations, expandable via external RAM packs.
* '''Logic''' – Utilizes a combination of discrete logic and custom chips for video output and keyboard scanning.

=== Video generation ===
The ZX Spectrum generates video using a technique called "bit-banging," where the Z80 CPU directly controls the display output. The screen resolution is '''256×192 pixels''' with a palette of 15 colors, plus black. The unique attribute system allows for color attributes to be assigned to 8×8 pixel blocks, resulting in colorful graphics but also potential color clash.

== 💾 Storage ==
Data is loaded and saved via a standard cassette tape interface operating at '''300 baud'''. The average loading time for a game is approximately 3-5 minutes, depending on the size of the program.

== 🔌 I/O and Expansion ==
* '''Edge connector (50-way)''' – provides access to the full Z80 bus, power, and video signals.
* '''9 V DC input''' – unregulated power supply.
* '''Composite video output''' – for connecting to monitors and TVs.
Commercial peripherals included:
: ''ZX Printer, joystick interfaces, and various RAM expansion packs.''

== 🔧 Known PCB Revisions & Errata ==
{| class="wikitable styled-table" style="width:70%; text-align:center;"
|+'''ZX Spectrum PCB Revisions'''
! Issue !! Visible Clues !! Key Fixes / Changes
|-
| '''Issue 1''' (1982) || Original board layout with no solder mask. || • Early boards had issues with RAM stability; later revisions improved power distribution.
|-
| '''Issue 2''' (1983) || Added solder mask and improved trace routing. || • Enhanced video output stability and reduced color clash issues.
|}

== 🛠️ General Maintenance ==
{| class="wikitable styled-table" style="width:70%; text-align:center;"
! Issue !! Cause !! Remedy
|-
| Flickering display || Aging capacitors in the power supply || Replace with high-quality electrolytic capacitors.
|-
| Unresponsive keys || Worn rubber contacts on the keyboard || Replace keyboard or use conductive paint to restore contact.
|-
| Loading errors || Dirty cassette connectors || Clean connectors and ensure proper tape alignment.
|}

Regular maintenance, including cleaning the keyboard and ensuring proper connections, can help prolong the life of the ZX Spectrum.

== 📜 Schematic & PCB ==
The complete schematic for the ZX Spectrum is available for enthusiasts and repair technicians.
{| class="wikitable"
|+
! [[File:ZX_Spectrum_Schematic.png|thumb|center|500px|ZX Spectrum circuit diagram]]
! [[File:ZX_Spectrum_PCB_Top.jpg|thumb|center|260px|Top view of the ZX Spectrum PCB]]
|}

== 🔧 Common Modifications ==
* '''RAM upgrade''' – Adding external RAM packs to increase memory capacity.
* '''Composite video mod''' – For improved video output quality on modern displays.
* '''Keyboard replacement''' – Upgrading to a full-travel keyboard for better typing experience.
* '''Turbo mode modification''' – Overclocking the Z80 for faster performance (requires careful tuning).

== 🔢 ROM Keyword Map ==
Each key on the ZX Spectrum keyboard has multiple functions depending on the mode:
{| class="wikitable styled-table" style="text-align:center;"
|+ Example ZX Spectrum keyboard layer
|-
! Key !! <code>F</code> mode !! <code>K</code> mode !! <code>L</code> mode
|-
| '''P''' || <code>PRINT</code> || <code>P</code> || <code>(</code>
|-
| '''R''' || <code>RETURN</code> || <code>R</code> || <code>)</code>
|-
| '''G''' || <code>GOTO</code> || <code>G</code> || <code>></code>
|}

== 🔗 Edge-Connector Pin-out ==
<templatestyles src="Template:StyledTable/styles.css" />
{| class="wikitable styled-table" style="width:75%; text-align:center;"
|+'''ZX Spectrum 50-way Expansion Bus (viewed from rear, component side up)'''
! Pin !! Signal !! Description !! Pin !! Signal !! Description
|-
| 1 || '''A15''' || Address bus MSB || 26 || '''D4''' || Data bit 4
|-
| 2 || '''A14''' || || 27 || '''D5'''
|-
| 3 || '''A13''' || || 28 || '''D6'''
|-
| 4 || '''A12''' || || 29 || '''D7'''
|-
| 5 || '''A11''' || || 30 || '''BUSACK''' || Bus acknowledge
|-
| 6 || '''A10''' || || 31 || '''BUSRQ''' || Bus request
|-
| 7 || '''A9''' || || 32 || '''WAIT''' || Insert wait-states
|-
| 8 || '''A8''' || || 33 || '''HALT'''
|-
| 9 ||