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| colours = 15 (2 per 8×8 cell) | | colours = 15 (2 per 8×8 cell) | ||
}} | }} | ||
The ZX Spectrum +3 was released on the 16th of May 1987. It is a significant redesign from the original [[ZX Spectrum | 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: | * ROM: 64kB ROM. 2×32kB EPROM arranged in 4 pages of 16kB. | ||
* RAM: | * RAM: 128kB of Dynamic RAM, arranged in 8 pages of 16kB. | ||
* Graphics: | * 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# | 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 | 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 | 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 --> |