Disk ROM
This page was last modified 09:23, 21 May 2022 by Gdx. Based on work by Sd snatcher and Mars2000you and others.

A Disk-ROM is the system software to acces to the disks. MSX standard Disk-ROM allows it via its BIOS, MSX-DOS Kernel or the Disk BASIC. Only computers sold with a floppy disque drive have Disk-ROM.

There are two major versions of Disk-ROM for MSX computers. There is also a version for Nextor that is an improved MSX-DOS 2.

Disk software takes space in RAM to create a disc Communication Area. To prevent the installation of disks, you must press the SHIFT key until you hear a beep during the initialization of the MSX. This can be used to use tape software for example.

There are drives that use another ROM type such as Quick-Disks for example. It works entirely different.

Disk-ROM 1.xx

The Disk-ROM 1.xx is a 16kB ROM that contains the MSX-DOS 1 kernel and a disk driver (for floppy disque drive in general).

It requiers 64kB RAM (16kB on each page and without Memory Mapper on MSX1, except if it is a MSX1 compatible Memory Mapper) to run the MSX-DOS or 32kB for the Disk BASIC.

Disk-ROM 2.xx

The Disk-ROM 2.xx is a 64kB ROM that contains the Disk-ROM v1.8, MSX-DOS 2 kernel and a disk driver, the Disk BASIC 2 and extensions. The disk driver is optional.

It requiers 128kB RAM (128kB RAM in the same slot so with a standard Memory Mapper) to run the MSX-DOS 2 and the Disk BASIC 2.

At startup, the system installs Disk-ROM 1 when the disk is formatted under MSX-DOS 1 or Disk-BASIC 1. You can also force the installation of Disk-ROM 1 by pressing the 1 key. This can be useful for formatting a disk for MSX-DOS 1 or Disk-BASIC 1.

Nextor Disk-ROM

Nextor Disk-ROM is a 128kB ROM. It's an improved Disk-ROM 2 mainly for the FAT16 support. It also adds several functionalities.

It requiers 128kB RAM (in the same slot so with a standard Memory Mapper) to run the MSX-DOS 2 and the Disk BASIC 2.

See also Nextor DOS.