This page was last modified 11:49, 21 August 2018 by Sylvester. Based on work by Eugeny Brychkov and Mars2000you and others.

GR8NET is a combo cartridge for MSX with Network as its main function. It has 8 distinctive mapper modes and seven composite mapper modes.

Since serial number 6C, GR8NET has a native stereo out. You can also use a switch to let only the PSG signal go out of the MSX audio out and the other sound expansions through the native stereo 3.5 mm jack output of the GR8NET.

GR8NET has SD-card interface accessible through internal _NET commands (FAT32/FAT16) and through Nextor (in combined mapper modes - FAT16/FAT12); several multimedia devices - MSX-Music, MSX-Audio, and SCC. Can operate in MP3 media player mode playing MP3 files or online streams (internet radio).

The cartridge operates in primary slot (all mapper modes) and sub-slot (except all composite mapper modes when slot expansion is performed internally), in all MSX models.

GR8NET developer, Eugeny Brychkov, is a developer of platform called GR8BIT.



  • RJ-45 UTP Ethernet connection, 10/100 Mbit auto-negotiation / auto MDI, IPv4
  • TCP, UDP, RAW and HTTP communication protocols
  • Built-in simple web browser to browse web server directory tree
  • DHCP configuration, DNS auto-resolution
  • 3 user programmable sockets
  • MSX-BASIC extended command support
  • Built-in terminal and telnet application
  • Built-in HTTP-based bload application
  • Operation as 1 Megabyte mapped RAM
  • ROM mapper emulation (plain, Konami)
  • Built-in SCC/SCC+ for standalone and Konami implementations
  • Hardware accelerated functions:
    • Interrupt generator using time period or frequency, with watchdog
    • PCM buffered 8- and 16-bit mono and stereo performance
    • Data prefetch from onboard RAM, ROM and W5100
    • Micro-SD card interface
    • Mathpack for FAT16/FAT32 and 32-bit multiplication and division
  • Native stereo output since serial number 6C
  • Mixed GR8NET mapper 512K, Mapped RAM 512K mode plus Nextor with SDC support
  • RAM-disk 2KB to 720KB, user programmable size
  • Operates at standard 3.58 MHz as well as at overclocked 7.11 MHz bus speeds
  • Built-in OPLL (YM2413, MSX-MUSIC) with its ROM BIOS (in mapper mode 8)
  • Built-in OPL-1 with ADPCM (Y8950, MSX-AUDIO)
  • MP3 audio streaming from network and SD-card
  • TCP/IP UNAPI version 1.0 implementation
  • GR8cloud virtual volume through Nextor in composite mapper modes

Mapper modes

  1. GR8NET
  2. Plain 32K ROM
  3. Konami without SCC (K4)
  4. Konami with SCC/SCC+ (K5)
  5. ASCII-8
  6. ASCII-16
  7. Mirrored ROM
  8. 1MB mapped RAM

Composite mapper modes

In these mapper modes GR8NET performs internal slot expansion, thus it must be installed into primary slot.

  • In mapper mode 8 subslot 0 is having 512K GR8NET mapper, subslot 1 is having 512K mapped RAM, subslot 2 is having Nextor driving SD-card and GRcloud virtual volume, and subtlot 3 is having MSX-Music BIOS;
  • In mapper modes 9-14 substlots 0-2 are having identical allocation as for mapper mode 8, but subslot 3 is having respective game mapper from the list above.
  • Mapper mode 15 is not valid.


  1. In mapper modes 9-14 game mappers share space with GR8NET mapper, while game mappers are read-only for applications running within them, the contents of ROM can be changed (or corrupt) through GR8NET mapper;
  2. Mapped RAM can be disabled for composite mappers (some games/applications will not work properly if machine's main RAM is in same slot as game mapper).