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ZX Spectrum +2A/2B, +3/3B: Difference between revisions

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Proper name of Spectrum 128
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| colours = 15 (2 per 8×8 cell)
| colours = 15 (2 per 8×8 cell)
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The ZX Spectrum +3 was released on the 16th of May 1987. It is a significant redesign from the original [[ZX Spectrum+ 128K|"Toastrack" 128K]] and [[ZX Spectrum +2|Grey +2]] models, with additional memory paging capabilities to support [[CP/M]] and additional ROM containing the [[+3DOS]] disc operating system code. The +3 has an integrated 3″ single sided floppy disc drive.
The ZX Spectrum +3 was released on the 16th of May 1987. It is a significant redesign from the original [[ZX Spectrum 128]] and [[ZX Spectrum +2]] models, with additional memory paging capabilities to support [[CP/M]] and additional ROM containing the [[+3DOS]] disc operating system code. The +3 has an integrated 3″ single sided floppy disc drive.
The "Black +2" appeared soon after with an integrated tape drive. Housed in a slightly modified version of the +2 case moulding cast in black plastic instead of grey.
The "Black +2" appeared soon after with an integrated tape drive. Housed in a slightly modified version of the +2 case moulding cast in black plastic instead of grey.


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=====Common hardware specifications=====
=====Common hardware specifications=====
* Processor: Zilog Z80A microprocessor clocked at 3.5469MHz.
* Processor: Zilog Z80A microprocessor clocked at 3.5469MHz.
* ROM: 64KB ROM. 2×32KB EPROM arranged in 4 pages of 16KB.
* ROM: 64kB ROM. 2×32kB EPROM arranged in 4 pages of 16kB.
* RAM: 128KB of Dynamic RAM, arranged in 8 pages of 16KB.
* RAM: 128kB of Dynamic RAM, arranged in 8 pages of 16kB.
* Graphics: 256 × 192 pixels, 16 colours, attribute based. See [[Spectrum Video Modes]].
* Graphics: 256×192 pixels, 16 colours, attribute based. See [[Spectrum Video Modes]].
* Sound: AY-3-8912 3 channel, 8 octave Programmable Sound Generator and "beeper". Modulated onto video signal.
* Sound: AY-3-8912 3 channel, 8 octave Programmable Sound Generator and "beeper". Modulated onto video signal.
* Keyboard: 58 plastic keys with metal springs, operating a plastic membrane.
* Keyboard: 58 plastic keys with metal springs, operating a plastic membrane.
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==Timings and Contention==
==Timings and Contention==
The contention and ram timings on the +3 and Black +2 differ significantly from earlier models due to the redesigned [[The Amstrad gate array|gate array]]. Timing patterns and memory contention are described in detail in the [[Contended memory#Black +2 (+2A/B) and +3|contended memory]] article.
The contention and ram timings on the +3 and Black +2 differ significantly from earlier models due to the redesigned [[The Amstrad gate array|gate array]]. Timing patterns and memory contention are described in detail in the [[Contended memory#Spectrum +2A, +3, +2B, and +3B|contended memory]] article.




==Paging==
==Paging==
The memory space is divided into four 16k pages and can be used in two ways; "Standard paging mode" and "Special paging mode".  
The memory space is divided into four 16kB pages and can be used in two ways; "Standard paging mode" and "Special paging mode".  
Paging is controlled by performing I/O writes to ports 0x1ffd and 0x7ffd.
Paging is controlled by performing I/O writes to ports 0x1ffd and 0x7ffd.


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====Standard paging mode====
====Standard paging mode====
The 64k of ROM and 128k of RAM can be paged into the memory space as shown in the diagram below:  
The 64kB of ROM and 128kB of RAM can be paged into the memory space as shown in the diagram below:  


<!-- table of memory pages -->
<!-- table of memory pages -->