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 and can even replace a hard drive!

Description

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

Specifications:

Supports MMC and compatible cards
.SYS driver for DOS
Now also available with a boot ROM (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:

If you order item # SDCART: Assembled PCB (without boot ROM), ready to use with sdcart.sys.
If you order item # SDCART-BOOT: Assembled PCB, with programmed boot ROM (latest version 0.41) installed in a socket.

See Download(s) & Link(s) below for links to the project page, where you can get the driver, boot ROM and other tools.

^[1] The boot ROM is installed in a socket (a quality one with machined pins) so you can replace it with a newer one or your own. Due to the height of the socket, it won't fit a cartridge unless you cut an opening. If you would like the boot ROM to be soldered directly to the board, please contact us. We will do it for the same price as the version with a socket. (Item #SDCARTJR-BOOT, see ordering section for pricing).

If you already own an SD-Cart JR and would like to add a boot ROM (or upgrade), we also sell pre-programmed EPROMS.

^[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.

Ordering

Buy here

In stock : Ships within 5 business days unless noted otherwise (out of stock, pre-order, holidays, etc).

The raphnet online store is temporarily closed for 3 weeks, from May 27 (2026) to June 17. Orders placed before May 27 will be shipped normally.

If you would like to receive a notification when we re-open, please send an e-mail to shop+open@raphnet-tech.com. Consult the relevant FAQ entry for more information.

Item #	SDCARTJR
Description	Card reader cartridge PCB for PCjr (Tested, No boot ROM)
Price	$35.99
Country of origin	China

Item #	SDCARTJR-BOOT
Description	Card reader cartridge PCB for PCjr (With boot ROM, tested)
Price	$43.77
Country of origin	China

We normally ship within 5 days (excluding week-ends and holidays) after payment.
Prices are in US dollars and are subject to change without notice.

Compatibility list

IMPORTANT: This is not a complete list. If something 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 support@raphnet-tech.com
Thanks!

Tested cards

Show list...

Model	Tested by	Supported
MMC, Lexar 64 MB	raphnet.	Yes
SD, Panasonic 8 MB	raphnet.	Yes
SD, Transcend 2 GB	raphnet.	Yes
SD, Toshiba 2 GB	raphnet.	Yes
Micro SD (with adapter), SanDisk 16 GB	raphnet.	Yes

Tested computers

Show list...

System	Tested by	Supported	Comments
IBM PCjr	raphnet.	Yes
IBM JX	-	Unknown / Not tested	If you test, please let us know!

FAQ

Q: Which version do I need? With or without a boot ROM?
A: The version with a boot ROM can, as the name implies, be used for booting. If you do not already boot using a hard drive (jr-IDE for instance), this is probably the version you should get. The boot ROM installs BIOS extensions to handle hard drive access and will work with fdisk and format. The version without a boot ROM, on the other hand, requires a driver. You will need to load sdcart.sys from your config.sys file. With this driver, the card will be assigned to the first free drive letter. (For instance, if you already have C:, the card will be D:)