SD Mapper V1 - MSX SD Card & Memory Mapper 512k

What is it?

The SD-Mapper V1 is a dual-slot SD card interface and 512KB RAM expansion cartridge for all MSX computers. It turns standard SD cards into MSX-compatible hard disks while simultaneously upgrading your system's memory — two essential upgrades in one cartridge.

Storage

Dual SD slots: 1× full-size SD + 1× micro-SD

Up to 4GB per card — entire MSX software library fits with room to spare

NEXTOR BIOS v2.1.1 — modern, fast, actively maintained DOS kernel

FAT12 / FAT16 support — prepare cards on any Windows/Mac/Linux PC

Memory — Two Modes, One Cartridge

The on-board 512KB RAM is switchable via physical toggles to match your needs:

SD + MegaRAM mode (S1 ON, S2 OFF): Load ROM games directly into RAM and run them without the original cartridge. Ideal for MSX2/2+ systems with 128K+ base RAM who want to play ROM dumps.

SD + Memory Mapper mode (S1 ON, S2 ON): Expand system RAM for MSX1/MSX2 machines with 64K-128K, enabling full NEXTOR functionality. Required for machines with less than 128K to access all DOS features.

Why did you make it?

Physical floppy disks die. SCSI hard drives are museum pieces. SD cards are cheap, reliable, and sold at every corner store. This cartridge solves the storage crisis while fixing the memory bottleneck that locks most MSX1 users out of modern software.

The dual-mode RAM is the key advantage. Some users need Mapper expansion to run NEXTOR properly on 64K MSX1 machines. Others want MegaRAM to play ROM dumps without original carts. This cart does both — flip two switches, change the personality. No firmware reflashing, no software configuration.

What makes it special?

Two upgrades, one slot — SD hard disk + 512K RAM expansion. Leaves your second cartridge slot free for sound modules (FMPAC, SCC, OPL) or graphics carts.

Physical mode switching — Two switches, two modes, instant change. No jumper mess, no reflashing.

Ready out of the box — Includes a 1GB MicroSD card with sleeve, pre-loaded with necessary system files. Insert and boot.

Acrylic case included — No bare PCB. Clean, protected, desk-friendly.

NEXTOR v2.1.1 — Latest stable kernel, better memory handling than legacy MSX-DOS2.

Works with SofaRun — Pair with any MSX system running SofaRun and browse your game collection with a joystick, zero command line.

Compatibility

All MSX models — MSX1, MSX2, MSX2+, turbo R

MSX1 with less than 128K RAM: Must use Memory Mapper mode (S1=ON, S2=ON) for full NEXTOR functionality

MSX2/2+ with 128K+ base RAM: Use MegaRAM mode (S1=ON, S2=OFF) for direct ROM loading, or Mapper mode for maximum system RAM

In the Box

Assembled SD-Mapper V1 cartridge in acrylic case

1GB MicroSD card with protective sleeve (pre-loaded with system files)

Pre-flashed with NEXTOR BIOS v2.1.1

Full-size SD card optional — slot ready for your own card.

SD-Mapper V1 vs V2 — Which to Choose?

SD-Mapper V1 (This Product) has dual RAM modes: both Memory Mapper and MegaRAM, switchable via toggles. Full-size + micro-SD slots. Best if you want maximum flexibility — switch between Mapper and MegaRAM as your needs change.

SD-Mapper V2 has Memory Mapper only. Full-size + micro-SD slots. Best if you only need Mapper expansion and prefer a streamlined single-mode design.

Both versions include acrylic case, NEXTOR v2.1.1, and are compatible with all MSX models.