SpectraVideo 318
The SpectraVideo 318 is the first model of the SpectraVideo range of computers and is considered to be a blue-print of the MSX standard of computers. The hardware and built in software are largely compliant with the MSX standard, but there are slight differences.
The SVI 318 is also close enough to the ColecoVision standard that SpectraVideo produced the SV-603 ColecoVision Game Adapter that allowed the users to run ColecoVision game cartridges.
Technical specifications:
- CPU: Zilog Z80A @3.58MHz
- ROM: 32KByte (16K BIOS and 16K for BASIC)
- RAM: 16KByte
- VRAM: 16KByte
- Video Display Processor (VDP): TMS9918
- Sound Chip: AY-3-8910
- Programmable Peripheral Interface: Intel 8255
CPU - The Zilog Z80
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.
Originally the Z80 was intended for use in embedded systems, just as the 8080 CPU. But the combination of compatibility, superior performance to other CPUs of the era, and the affordability led to a widespread use in arcade video game systems, and later in home computers such as the Osborne 1, TRS-80, ColecoVision, ZX Spectrum, MSX, Sega's Master System and many more. The Z-80 ran the original Pac-Man arcade cabinet. The Z-80 was used even in the Game Gear (1990s), and the TI-81 and succeeding graphic calculators.
The Z-80 remained in production until June of 2024, 48 years after its original release. Zilog replaced the processor with its successor the eZ80, an 8-bit microprocessor that features expanded memory addressing up to 16 megabytes, and running up to 50MHz, comparable to a Z80 clocked at 150MHz.
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
Sound - The AY-3-8910 PSG
The AY-3-8910 is a 3-voice Programmable Sound Generator, or PSG. It was designed by General Instruments 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 -
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.
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.
VRAM: 16kB
32x24 16 color text, pattern based
256x192 16 color, 2 color per 8 pix.
