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ZX Spectrum +2A/2B, +3/3B: Difference between revisions
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Use proper multiply symbols
(lots of stuff about motherboards) |
(Use proper multiply symbols) |
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| rom = 64kB | | rom = 64kB | ||
| ram = 128kB | | ram = 128kB | ||
| rampage = | | rampage = 8×16kB | ||
| manu = Amstrad | | manu = Amstrad | ||
| volume = | | volume = | ||
| resolution = | | resolution = 256×192 | ||
| colours = 15 (2 per | | 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 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 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. | ||
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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. | * 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 | * 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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The three disc controller signals generated by the gate array are placed on the expansion port so that an external floppy disc controller could be connected to a +2A to provide the functionality of the omitted internal components. Amstrad planned to release this as the ''SI-1'' but it never went on sale. | The three disc controller signals generated by the gate array are placed on the expansion port so that an external floppy disc controller could be connected to a +2A to provide the functionality of the omitted internal components. Amstrad planned to release this as the ''SI-1'' but it never went on sale. | ||
=====+2B | =====+2B and +3B===== | ||
The +2A/+3 circuit contains a design flaw in the audio output circuitry which causes serious distortion to AY-3-8912 music. A new design was developed in 1988 with redesigned audio circuits and manufactured as the +2B and +3B. Unlike the +2A/+3, Amstrad did not create one common motherboard for these computers. Instead the +2B board is stepped on the right hand side to allow two boards to be panellized side by side and use a much smaller area (hence cheaper to produce) than two +2A/+3 boards. | The +2A/+3 circuit contains a design flaw in the audio output circuitry which causes serious distortion to AY-3-8912 music. A new design was developed in 1988 with redesigned audio circuits and manufactured as the +2B and +3B. Unlike the +2A/+3, Amstrad did not create one common motherboard for these computers. Instead the +2B board is stepped on the right hand side to allow two boards to be panellized side by side and use a much smaller area (hence cheaper to produce) than two +2A/+3 boards. | ||
The identification of models is regularly confused because Amstrad sold large numbers of computers with a Z70833 motherboard (+2B) in cases that were moulded for the +2A. The change to shipping +2B motherboards instead of +2A boards appears to have happened fairly early on because most +2A cases encountered contain a +2B motherboard. Z70830 motherboards populated as a +2A are consequently quite rare. | The identification of models is regularly confused because Amstrad sold large numbers of computers with a Z70833 motherboard (+2B) in cases that were moulded for the +2A. The change to shipping +2B motherboards instead of +2A boards appears to have happened fairly early on because most +2A cases encountered contain a +2B motherboard. Z70830 motherboards populated as a +2A are consequently quite rare. | ||
The +2B motherboard is the Z70833 ISSUE 1 | The +2B motherboard is the Z70833 ISSUE 1 or 2 ©1988. There is also an ISSUE 4 ©1990 which has a different FM modulator circuit for the audio (no example of an ISSUE 3 board has surfaced so it's possible none were ever produced/sold). | ||
The +3B motherboard is the Z70835 ISSUE 1 ©1988. Unlike the Z70830 it has no provision for connecting a datacorder but the connections for an external floppy controller remain on the expansion port. Unlike the +2A and +2B all +3 cases are the same. i.e there is no +3B case moulding. | The +3B motherboard is the Z70835 ISSUE 1 ©1988. Unlike the Z70830 it has no provision for connecting a datacorder but the connections for an external floppy controller remain on the expansion port. Unlike the +2A and +2B all +3 cases are the same. i.e there is no +3B case moulding. | ||
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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 ASIC|gate array]]. Timing patterns and memory contention are described in detail in the [[ | The contention and ram timings on the +3 and Black +2 differ significantly from earlier models due to the redesigned [[The Amstrad ASIC|gate array]]. Timing patterns and memory contention are described in detail in the [[Contended memory#+2A and +3|contended memory]] article. | ||
