Spectravideo SVI-838
This page was last modified 22:21, 1 December 2020 by Mars2000you. Based on work by NYYRIKKI and Rderooy and others.

Contents

Description

The SVI-838, also known as X'press 16, was the last MSX related microcomputer produced under Spectravideo brand. Spectravideo was a American company that was selling MSX computers in many countries while using Bondwell in Hong Kong as their hardware manufacturer. However SVI-838 was released in 1986 after Bondwell bought most of Spectravideo shares and closed Spectravideo American office.

Although SVI-838 is an IBM PC clone with CGA graphics, it also includes same video co-processor as MSX2 and MSX sound compatible PSG on system board. With separately sold SVI-811 Game Adapter it is possible to extend this machine to be partially MSX compatible game console. For more MSX related information, please see SVI-811 page.

Notes:

  • Specially modified GW-BASIC 3.2 (see below) was included with the system that gave somewhat limited access to extended sound and video chip capabilities.
  • Alternatively it was possible to use video co-processor VRAM as RAM disk or printer buffer by using drivers delivered with the machine.
  • The logo in front of system is not always the same, and there are also examples without sticker.

SVI-838 peripherals

  • SVI-109P: Quickshot IX joyball
  • SVI-???? : Quickshot X joystick (provided with the SVI-838)
  • SVI-811: Game Adapter
  • SVI-812: Multifunction card (adds 384kB RAM, RS-232C, RTC)
  • SVI-813: Cooler
  • SVI-814: PAL RF Adapter (to color TV or RGB monitor)
  • SVI-815: Monitor cable (D15 to 21 pins adapter, to RGB monitor)
  • SVI-816: Monitor cable (D15 to 8 pins adapter, to digital/analog RGB monitor)
Brand Spectravideo
Type SVI-838
Year 1986
Region
Original price
RAM 256kB, expandable to 640kB
VRAM 128kB for V9938, 16kB for V6355 (CGA video chip)
Media 5.25" 360kB floppy disks - With SVI-811: MSX cartridges
Video Yamaha V6355 (CGA) with superimposition over V9938 (MSX2 VDP!)
Audio AY-3-8912 28-pin PSG, PC Speaker
Chipset
Keyboard layout QWERTY (can be modified with keyboard driver)
Extras One or two 5.25" 360kB disk drives (or a drive and a 20MB hard disk drive), superimposing, Quickshot X joystick (not MSX compatible), enhanced version of GW-BASIC
Emulation ROM dumped, mainly for archival purposes. It is unknown if this can be emulated.

Gallery

Spectravideo SVI-838 with monitor
Spectravideo SVI-838 main PCB
Spectravideo SVI-838 inside
Spectravideo SVI-838 without sticker
Spectravideo SVI-838 front
Spectravideo Quickshot X joystick
SVI-838 front (close-up)
Spectravideo SVI-838 back

Specifications

The SVI-838 is a PC clone with an Intel 8088 CPU running at 4.77 MHz, but has also the PSG and VDP, making it a hybrid system, with even an enhanced version of GW-BASIC.

Additional or modified GW-BASIC instructions for sound and graphics

  • COLOR background color
  • NOISE channel, periode, duration to use the PSG noise channel
  • PAINT x,y, paint attribute, border color, background attribute
  • PLAY with music macro language for each of the 3 PSG channels
  • SCREEN mode, burst, active page, visible page, clear screen, superimposition
  • SOUND frequency, tempo, volume, channel
  • SOUND OFF to select the PC generator sound
  • SOUND ON to select the PSG and use PLAY in similar fashion to Tandy and PCjr computers

Connections

  • RGB connector for monitor
  • Analog sound & Composite video (B/W)
  • Keyboard connector
  • Centronics compatible Parallel port for a printer
  • PC Mouse / Light Pen connector
  • Game connector for the provided PC joystick
  • ISA compatible expansion slot (for SVI-811A, SVI-812 or 3rd party expansion card)

I/O Device map

I/O Device SVI-838 SVI-811
8237A-5 DMA chip 000-00F
8259A Interrupt 020-021
8253-5 Timer 040-043
8255-5 PPI 060-063
DMA Page Registers 080-083
NMI Mask Register 0A0-0AF
Game Control 200-20F
Paraller Printer 378-37F
V9938 3C0-3C3 98-9B
PSG 3C8-3CA A0-A2
V6355 3D0-3DF B0-B7
Disk 3F0-3F7

Tips n' tricks

Due to fact that CGA graphics are superimposed over V9938, in order to play Japanese/USA games on original 60Hz frequency both V9938 and V6355 need to be changed to 60Hz mode.

60Hz pseudocode:
SVI-838: OUT #3C1,#80:OUT #3C2,#89:OUT #3DD,#65:OUT #3DE,1
(SVI-811: OUT #99,0:OUT #99,#89:OUT #B5,#65:OUT #B6,0)

50Hz pseudocode:
SVI-838: OUT #3C1,#82:OUT #3C2,#89:OUT #3DD,#65:OUT #3DE,9
(SVI-811: OUT #99,2:OUT #99,#89:OUT #B5,#65:OUT #B6,8)

External links