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The SCSI Hard Drive Emulator for retro computing.



  1. downloads for v3/v4/v5 hardware revisions.
  2. downloads for v6 hardware revisions. This firmware will NOT work on the older boards.


[31 Jan 2018]v6.1.3 Bugfix release

  • Fixes several synchronous transfer bugs, especially write issues at 10MB/s

[28 Nov 2017]v6.1.2 Bugfix release

  • Fix several synchronous negotiation bugs

[21 May 2017]v6.1.1 Bugfix release

  • Fix scsi2sd-util size and sector-size inputs
  • Fix crash when configured scsi disk starting sector is less than SD card size
  • Add new "turbo" speed option to boost speeds.
    • May not be reliable, and use is not supported
    • Async timings trimmed
    • Sync speeds boosted to theoretical 15.625MB/s, with 12.0MB/s measured read throughput
    • SD card put in "high speed" mode.
    • USB for configuration/firmware updates is disabled in turbo mode when processing SCSI commands. A power cycle may be required to connect again via USB

[1 May 2017]v4.7.1 Bugfix release

  • Fix scsi2sd-util size and sector-size inputs
  • Fix crash when configured scsi disk starting sector is less than SD card size

[2 April 2017]v6.1.0 Bugfix release

  • Enable sync transfers on SCSI1 hosts
  • Support 4MB/s sync transfers for Amiga A590 (WD33C93)
  • Merge v4.7 release changes

[12 March 2017]v4.7 New firmware

  • Fix bug in SCSI Inquiry command for SCSI2 hosts
  • Added OMTI host quirks mode
  • Fix for booting from early Mac Plus ROMS
  • Performance fix when SCSI2 mode is enabled. Some users may need to disable SCSI2 mode if it was incorrectly enabled previously.
  • Added support for configurable mode pages
  • Fix for exporting selectionDelay/startupDelay parameters to XML via scsi2sd-util
  • scsi2sd-util is now built with libudev1 on Linux, as all distros have moved to this version. Users on older Linux distributions will need to compile from source.

SCSI2SD Archived News


SCSI2SD is an emulator for old SCSI hard drives. It allows replacing one or several old broken SCSI drives with a SD memory card.

Which version should you buy ?

SCSI2SD V5 This is the stable version, with the widest compatibility. Most people should buy this version. It works well with both SCSI1 and SCSI2 systems.
SCSI2SD V6 This board offers better performance, but is more expensive.
  • It may not work properly in SCSI1 systems, including any system using DB25 cabling or passive terminators.
  • It requires more power than the V5 board and may not be stable using the scsi cable terminator power alone.
  • See SCSI2SD V6 Compatibility
SCSI2SD for Powerbook Designed for Apple Powerbook laptops using 2.5" drives.


The new V6 board and 2.5" PowerBook version are available at:

The 3.5" boards are available from the following distributors:

3rd party accessories

  • Internal faceplates for V5 and V6 boards, and external V5 case.
  • Thingiverse nibblernibbles has created a 3d-printable external enclosure for the SCSI2SD + DB25 adapter. Power can be supplied over USB for hosts which don't supply termination power.
  • SCSI2SD V5 & V6 Bracket by Maya Designs


  1. In-built active terminator.
  2. Emulates up to 4 SCSI devices (7 for the V6 version)
  3. Supports sector sizes from 64 bytes to 8192 bytes
  4. Firmware updatable over USB
  5. Highly configurable over USB
    • Selectable SCSI ID
    • Selectable parity support
    • Enable/disable Unit Attention Condition
    • Artificial limits on the SCSI disk size (eg. limit size to 4G to avoid OS bugs)
    • Sector size (can also be set via the SCSI MODE SELECT command, as sent by SCSI format utilities).
  6. External LED connector.

Technical Specifications

V5 hardware V6 hardware
SCSI Interface SCSI-2 Narrow 8-bit 50-pin connector.

Supports asynchronous transfers only.

SCSI-2 Narrow 8-bit 50-pin connector.

FAST10 (10MB/s) synchronous transfers.

SD Card Interface microSD, tested up to 64GB

Communication is via the SPI protocol at 25MHz (3MB/s theoretical max)

Full-size SD, tested up to 32GB

Up to 20MB/s

USB Interface Firmware updates and configuration

USB 2.0 micro-B

Firmware updates, configuration, and mass-storage

USB 2.0 micro-B. Mass-storage at USB 2.0 FS speeds (1.2MB/s max)

Power 5V via standard Molex 4-pin drive connector, USB, or self-powered using the SCSI host termination power.

2.35W maximum (500mA)

DO NOT CONNECT 12V at all if you need to make your own power cable as it risks destroying the board if you accidentally swap the wires.

5V via floppy 4-pin drive connector, USB, or self-powered using the SCSI host termination power.

2.35W maximum (500mA)

Dimensions (L x W x H) 5cm x 10cm x 1.5cm 10cm x 9cm x 1.5cm

Tested under optimal conditions. For comparison, here are some benchmarks of some older SCSI hardware.

Up to 2.6MB/s read, 2.3MB/s write. Up to 10MB/s.



Firmware update utility and configuration tool at:

  1. downloads for v3/v4/v5.
  2. downloads for v6.

These files are currently available for Windows, Linux, and Mac OSX.

A copy of all sources can be obtained via the command:

git clone --recursive git://

or (for V6)

git clone --recursive git://

Alternatively, the git sources can be viewed using your web browser by clicking here or here (V6)


Alternative Open SCSI Projects

  • AJ's alternative implementation. AJ and I originally had a competition to design and build a SCSI device to boot an old Mac LCIII. The deadline for that competition has long-since expired without a winner, but we have both continued to progress our designs.
  • S2I (was: SCSI2IDE)
  • AVR based SCSI RAM disk


For historical project information see SCSI2SD old