Sega Sega Computer
Sega SC 3000
sega_sg3000

Sega SC-3000

The SC-3000 is a computer designed by SEGA and was released in July of 1983 in Japan. It is very similar to the Sega Console SC-1000, which has an optional keyboard to function as a home computer. With the SC-3000 Sega wanted to establish a greater presence in the home computer market. The computer was released in Japan, Australia, France, Italy, Finland and New Zealand. It faced stiff competition from the established brands like Commodore and Atari.

The computer has a very small 2kByte RAM. The machine only functions if a ROM or an expansion RAM cartridge is inserted. The architecture is not unlike that of the MSX standard which uses the TMS9918 as the video display chip, and a Z80 CPU running at 3.58MHz. For audio the SC-3000 uses the SN76489A, a 3 channel, 1 white noise Programmable Sound Generator. There is an RF output, an audio and composite video output as well as an RGB video output on the Yeno model.

The SC-3000 came in three colors, red, black and beige. Sega later released an upgraded SC-3000H which is the same machine but has a better keyboard.

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

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.

Technical Details
Released 1986
Country Japan
Brand Sega
Type Sega Sega Computer
Name Sega SC 3000
CPU Class Z80
CPU Z80 @3.58MHz
Memory RAM: 2kB
RAM max: 64kB
VRAM: 16kB
Sound Chip SN76489 PSG
Sound PSG: 3 Square waves, 1 noise generator
Display Chip TMS9918
Display 256x192 in 16 Colors
Best Text 40x24
Best Color 16 Colors
Graphics 256x192
Sprites 32 sprites, 4 simultanuously
Storage ROM Cartridges, Cassette Tape
Original Price ¥29,500
External Links 🌐
Sega SC-3000
Wikipage for the Sega SC-3000
WikiPedia: The TMS9918 Video Processor
Wikipedia page about the TMS9918 Video Display Controller (VDC) used in many computers such as MSX, ColecoVision, Nabu, Sord, TI-99 and more
Z80 CPU
Wikipedia page on the very popular Z80 8-bit CPU used in many computers of the 1980's era.