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MSX SVI-728

The SVI-728, introduced in 1984, is the first Spectravideo home computer that fully complied with the MSX standard. The design is similar to the SVI-328, which did not fully implement the standard.

The SVI-728 has 64KByte of RAM, 1 cartridge slot on top and has a keyboard with a full numeric keypad

MSX was announced by Microsoft and the ASCII Corporation on June 16th 1983. It was marketed by Kasuhiko Nishi, who was Vice-President at Microsoft and a director at the ASCII Corporation. MSX was an attempt to create a hardware and software standard among various home computers, similar to what VHS had accomplished for the Home Video market.

The MSX Standard defines specifications for:
  • CPU and Memory
  • Video Output hardware
  • Audio hardware
  • Cassette and Disk drives
  • Keyboard, mouse and joysticks
  • Expansion and I/O ports
As a result, sofware and hardware are interchangable between machines from different manufacturers. The standard sets rules for the minimum, but manufacturers are free to expand beyond that and make their machines unique.

The standard became a success in Japan, with many big software houses such as Konami creating games for it. Outside of Japan, the adoption rate was low. In the USA, Microsoft actively pushed the PC compatibles, since they sold the operating system for it, and in Europe the MSX computers had stiff competition from Commodore and Atari. The Netherlands and Spain have the highest rates of MSX users in Europe.

MSX Cassette Pin Layout

The MSX Standard calls for all MSX computers to have a standard data-cassette port. This port transports the audio-in/out signals to and from the datarecorder and the computer has a relay-switch on board to turn the recorder on and off.

MSX Cartridge Connector

The MSX Cartridge system uses a 50-pin flat-edge connector to connect to the systems expansion bus. The cartridge slot maps into one of the main- or sub-slots.

TMS9918 Series Video Display Processor (99n8, 99n9, 91n8, 91n9)

The TMS9918 is a series of video display controllers (VDC) manufactured in 1979 by Texas Instruments, also refered to as 'Video Display Processor' (VDP). The TMS9918 and its variants were used in the ColecoVision, CreatiVision, Memotech MTX, MSX, NABU Personal Computer, SG-1000/SC-3000, Spectravideo SV-318, Spectravideo SV-328, Sord M5, Tatung Einstein, Texas Instruments TI-99/4, Casio PV-2000, Coleco Adam, Hanimex Pencil II, and Tomy Tutor.

Key Features:

  • 256x192 pattern based color pixels per screen
  • 16 different colors
  • 8-bit memory mapped CPU interface
  • No need for DMA, CPU can access VRAM
  • 32 single color Sprites per screen (4 per scanline)

Variants:

  • TMS9918A - 60Hz output, NTSC video
  • TMS9928A - 60Hz output, YPbPr video
  • TMS9929A - 50Hz output, YPbPr video
  • TMS9118 - Different RAM than TMS9918A, otherwise identical
  • TMS9128 - Different RAM than TMS9928A, otherwise identical
  • TMS9129 - Different RAM than TMS9929A, otherwise identical

Programmable Sound Generator (AY-3-8910 compatible PSG)

The AY-3-8910 is a 3-voice Programmable Sound Generator, or PSG. It was designed by General Instrumet in 1978 for use with their own 8-bit PIC1650 and their 16-bit CP1610 computers.

The PSG is widely used in many arcade cabinets, pinball machines, and many micro-computers. Here is a list of some of the major brands of computer that used the AY-3-8910:

  • Intellivision
  • Vectrex
  • Amstrad CPC range
  • Oric-1
  • Color Genie
  • Elektor TV Games Computer
  • All MSX-1 and MSX-2 computers
  • ZX Spectrum home computers

General Instrument spun of MicroChip Technology in 1987 and the chip was sold under the MicroChip brand, and licensed to Yamaha as the YM2149F which the Atari ST range of computers use. Functionally the PSG is very similar to the Texas Instruments SN76489.

Variants:

  • AY-3-8910
    Comes with 2 general purpose 8-bit parallel I/O ports, used for Keyboard and Joystick in for instance MSX.
  • AY-3-8912
    Same chip, but in a 28-pin package. Parallel port B is not connected to save cost and space.
  • AY-3-8913
    Same chip, but in a 24-pin package. Both parallel ports are not connected.
  • AY-3-8914
    The AY-3-8914 has the same pinout and is in the same 40-pin package as the AY-3-8910, except the control registers on the chip are shuffled around, and the 'expected input' on the A9 pin may be different. It was used in Mattel's Intellivision console and Aquarius computer.
  • AY-3-8930
    Backwards compatible but BC2 pin is ignored
  • YM2149F
    Yamaha Produced chip, same pin-out as the AY-3-8910, but pin 26 could halve the master clock. Can be used to replace the AY-3-8910 if pin 26 is left disconnected.
  • YM3439-D
    CMOS version of the Y2149 in 40-pin DIP
  • YM3439-F
    CMOS version of the Y2149 in 44-pin QFP
  • YMZ294
    Variant of the YM3249 in an 18-pin package. Parallel ports not connected, and all sound channels mixed on 1 port.
  • T7766A
    Toshiba variant of the AY-3-8910, fully compatible. Used in some MSX models.
  • Winbond WF19054, JFC95101, and File KC89C72: Fully compatible versions of the AY-3-8910 produced for slot machines.

Zilog Z80 CPU Family

The Z80 quickly became popular in the personal computer market, with many early personal computers, such as the TRS-80 and Sinclair ZX80, using the Z80 as their central processing unit (CPU). It was also widely used in home computers, such as the MSX range, SORD, and the Amstrad CPC, as well as in many arcade games. Additionally, it was also used in other applications such as industrial control systems, and embedded systems. The Z80 was widely used until the mid-1980s, when it was gradually replaced by newer microprocessors such as the Intel 80286 and the Motorola 68000.

The Z80 microprocessor was developed by Zilog, a company founded by Federico Faggin in 1974. The Z80 was released in July 1976, as a successor to the Intel 8080. It was designed to be fully compatible with the 8080, but also included new features such as an improved instruction set, more powerful interrupts, and a more sophisticated memory management system.

The Z80 quickly became popular in the personal computer market, with many early personal computers, such as the TRS-80 and Sinclair ZX80, using the Z80 as their central processing unit (CPU). It was also widely used in home computers, such as the MSX range, SORD, and the Amstrad CPC, as well as in many arcade games. Additionally, it was also used in other applications such as industrial control systems, and embedded systems. The Z80 was widely used until the mid-1980s, when it was gradually replaced by newer microprocessors such as the Intel 80286 and the Motorola 68000. The design was licensed to Synertek and Mostek as well as the European SGS.

The Z80s instruction set is binary compatible with the Intel 8080, so that 8080 code such as the CP/M Operating System and Intel's PL/M compiler for the 8080 can run unmodified on the Z80. The Z80 had many enhancements over the 8080 such as 16-bit data movement instructions, block copy and block I/O instructions, single bit addressing of all registers, IX/IY offset registers, better interrupt system and a complete duplicate register file for context switching during an interrupt.

Source: WikiPedia
Technical Details
Released 1984 Brand Spectra Video Type Spectra Video (SVI) Name SVI 728 CPU Class Z80 CPU Zilog Z80A @3.58MHz Memory RAM: 64kB
VRAM: 16kB
Sound Chip General Instruments AY-3-8910 Programmable Sound Generator Sound 3 wave channels + white noise Display Chip none Display 40x24 text
32x24 16 color text, pattern based
256x192 16 color, 2 color per 8 pix.
Best Text 40x24 Best Color 16 colors Best Graphics 246x192 in 16 colors Sprites 1 color, 16x16, 4/scanline, 32 total
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