SD-Cart JR: A card reader cartridge for the IBM PCjr

This cartridge PCB lets you use MMC/SD cards as a removable storage medium for your PCjr.

  •  Example use
  •  This product
  •  This product
  •  This product (back)
  •  Beveled PCB edge
  •  Example use


This product is a great alternative to floppies and can even replace a hard drive if used with the optional boot ROM.

  • Supports MMC and compatible cards
  • .SYS driver for DOS
  • Experimental boot ROM available (for booting from a card)[1].
  • Full size MMC Card slot, push/push type. (card not included)
  • Activity LED
  • Read speed: 44 kB/s, Write speed: 35 kB/s.[2]
  • Quality PCB with hard-gold fingers for durability.
  • Form-factor: PCjr cartridge PCB, fits standard cartridge shells if you cut some plastic. Sold without an enclosure.

What's included:
  • Assembled PCB (without boot ROM), ready to use with sdcart.sys.
See Download(s) & Link(s) below for links to the project page, where you can get the driver, boot ROM and other tools.
[1] To use the experimental boot ROM, you must supply and program your own EPROM and install it on the PCB (preferably with a socket). When a socket is used the PCB no longer fits in a cartridge. In the future, once the boot ROM is no longer experimental (i.e. once it has been confirmed to work correctly in many situations) we will also offer this product with a pre-installed EPROM.

[2] Faster than floppies (10 kB/s). Measured by reading/writing 100kB of data using the .SYS driver installed in fast (above 128k) memory. Performance may vary depending on the card used.


This item is sold and shipped from Japan. (Unlike most of our items which are from Canada) ?

Buy here

Out of stock

A new batch is planned for February or March 2021.
  • Send an e-mail to if you would like to be notified when this item becomes available.

DescriptionCard reader cartridge PCB for PCjr (tested and ready for use)
product picture

We normally ship within 5 days (excluding week-ends and holidays) after payment.

Compatibility list

IMPORTANT: This is not a complete list. If your controller or game does not appear here, it simply means that we did not get the chance (or the idea) to test it, or that no one let us know that it works.

Help us improve this page by sending test results by email to

Tested cards

Show list...
ModelTested bySupportedComments
MMC, Lexar 64 MBraphnet.Yes
SD, Panasonic 8 MBraphnet.Yes

Tested computers

Show list...
SystemTested bySupportedComments
IBM PCjrraphnet.Yes
IBM JX-Unknown / Not testedIf you test, please let us know!

Download(s) & Link(s)

Project page (English)Press here
Project page (French)Press here

Related products

Product photo

Set of 4 PCBs for making your own cartridges for the IBM PCjr computer.