Spectravideo SVI-727
This page was last modified 19:00, 19 April 2022 by Briqunullus. Based on work by Mars2000you and Gdx and others.



The Spectravideo SVI-727 is a cartridge that allows to use the 80 column text mode on a MSX1 computer, as it has the Hitachi HD6845 CRTC (Cathode Ray Tube Controller) that adds this mode. The included ROM only contains character data.

The cartridge was sold without software. To get it running, one would need the software provided with the Spectravideo SVI-707 diskdrive. It was mainly useful under CP/M, but it was also possible to use the MODE80.COM utility under MSX-DOS.

Both CP/M and MODE80.COM are written for the SVI-707 diskrom. Unfortunately this diskdrive has compatibility problems and works best on its intended host, the Spectravideo SVI-728. This limits the usability of the SVI-727 cartridge.

However, if programmed manually, the cartridge works on any MSX. It requires a second monitor or a monitor switch. The output is composite video in monochrome.

Note: There is also a model for SVI-318/328 computers under SV-806 reference.

Brand Spectravideo
Model SVI-727
Year 1984
Region Europe
Launch price IT: L. 295,000
NL: ƒ 499
Package content Cartridge, cable and manual
Emulation ROM dump made and emulated in blueMSX.


Spectravideo SVI-727 box-front
Spectravideo SVI-727
Spectravideo SVI-727 back
Spectravideo SVI-727 PCB front
Spectravideo SVI-727 PCB back

System Requirements

  • MSX1 computer with video composite output, one free slot cartridge

Internal Components

The HD6845 has 18 registers plus one for the register selection.

Port Description
78h To write to the register selection
79h To acces to the selected register (R0-R11 write only, R16-R17 read only)

There are also two other interesting chips:

  • a HM6116P-4 chip providing 2 kilobytes of CMOS Static RAM. The RAM is accessible on the addresses B800h-BFFFh.
  • a TMS2732AJL-45 chip providing 4 kilobytes of ROM. This ROM contains character data. It is not accessible from the MSX.