Sinclair+ZX81

a low-cost [|home computer] developed by Sinclair Research and manufactured in [|Scotland] by [|Timex Corporation], launched in the [|UK] in March 1981, and as slightly modified [|Timex Sinclair 1000] in the [|US] in July 1982. The ZX81 consists of a 3.5 MHz Z80A CPU from [|Nippon Electric Company], an [|ASIC] dubbed Sinclair Computer Logic, an 8 [|KiB] ROM with the [|operating system], the Sinclair BASIC interpreter, and one KiB of RAM, which could be expanded externally to 16 KiB. For I/O it had a [|membrane keyboard], a [|RF modulator] to output 24 lines x 32 [|characters] or 64x48 [|pixel] as [|signal] for a [|television], and a [|serial port] and [|softmodem], to store and load programs and data to or from an external [|audio cassette] [|recorder] with 250 [|baud].
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 * [[image:Sinclair_ZX81_Setup_PhotoManipped.jpg link="https://en.wikipedia.org/wiki/File:Sinclair_ZX81_Setup_PhotoManipped.jpg"]] ||~  || **Sinclair ZX81**, (ZX81, Timex Sinclair 1000)

[|Jim Westwood's] technical dodge using [|non-maskable interrupts] solved the flicker problem of the [|ZX80] and gave the ZX81 a "multi-tasking" SLOW mode with a steady display, slowing down programs fourfold. Z80 [|machine code] could be inlined at absolute addresses and called via USR or encoded in [|comment lines], which could be executed after some appropriate [|POKE] instructions. || toc =Chess Programs= The only chess program for the non expanded ZX81 in SLOW mode was 1K ZX Chess by David Horne. Other programs, such as Artic Computing's ZX Chess, and Chris Whittington's SuperChess, require the 16 KB memory expansion.
 * ZX81 setup ||~  ||^   ||


 * [[image:ZXChessIscreen.gif width="192" height="144" link="ZX Chess"]] ||~  || [[image:1kZXChess.JPG width="135" height="167" link="1K ZX Chess"]] ||~   || [[image:SuperChessScreen.gif width="256" height="192" link="SuperChess"]] ||
 * ZX Chess ||~  || 1K ZX Chess ||~   || SuperChess ||

=See also=
 * TRS-80
 * ZX Spectrum

=Publications=
 * [|ZX81 Assembly Instructions] (pdf)
 * [|ZX81 Assembly Instructions U.S. Version for UHF Channel 33] (pdf)
 * [|Brendon Gore] (**1982**). //[|Interview-One Degree In Artic]//. Your Computer, [|May 1982]
 * David Horne (**1982**). //[|ZX-81 Disassembler]//. Your Computer, [|July 1982]
 * [|Stuart Nicholls] (**1982**). //[|ZX-81 Games Writing]//. Your Computer, [|November 1982]
 * David Horne (**1982**). //[|Chess in 1K]//. Your Computer, [|December 1982]
 * David Horne (**1983**). //ZX-81 Chess//. Your Computer, [|January 1983]
 * David Horne (**1983**). //[|Full ZX-81 Chess in 1K]//. Your Computer, February 1983

=Forum Posts=
 * [|World smallest chess program] by Óscar Toledo Gutiérrez, [|comp.lang.c], November 22, 2006
 * [|Turnier: Schachcomputer vergleich zu alte Computerschach Spiele] by Spacious Mind, [|Schachcomputer.info Forum], August 12, 2008 (German)

=External Links= > [|Index of ZX81 Tapes by Artic] > [|Index of ZX81 Tapes by Mikro-Gen] > [|Index of ZX81 Tapes by Psion] > [|Index of ZX81 Tapes by Sinclair Research] > [|Index of ZX81 Tapes by Timex Sorted by Name]
 * [|ZX81 from Wikipedia]
 * [|ZX80 from Wikipedia]
 * [|Timex Sinclair 1000 from Wikipedia]
 * [|List of ZX80 and ZX81 clones from Wikipedia]
 * [|ZX81 Home Page]
 * [|Sinclair ZX81 Page]
 * [|ZX81 Museum - Sinclair ZX81 Hardware, Software and Literature]
 * [|ZX81 circuit diagram]
 * [|Assembly Listing of the Operating System of the Sinclair ZX81]
 * [|1K ZX81 Chess Z80 Assembly listing] © Copyright David Horne
 * [|Timex Sinclair 1000 - Old Home Computers Collection] from The Spacious Mind
 * [|ZX81 Software, Books and Hardware Collection]

=References= =What links here?= include page="Sinclair ZX81" component="backlinks" limit="40"
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