What is it?

This bootable expansion card provides a SD card interface to 8-bit ISA systems such as PC/XT, via an IDE interface and an SD adapter board. It is typically paired with a 64MB to 1GB SD card, or MicroSD with adapter. Silent, and more reliable than an old mechanical hard drive.

The SD adapter board with IDE 2.0mm male connector can be easily found in online shops like Aliexpress, I offer it as an option, guaranteeing that it works properly.

Due to the complexity of the routing being low profile and the positions of the components, also close together, the design of both is 4-layer, the two internal layers being GND and VCC.

A fault has been identified and corrected by cutting the track and a small bridge, as shown in the pictures. It is now working correctly.

Available in HASL finish or ENIG finish + Gold Fingers, if you do not intend to extract and insert the card many times (dozens of times), HASL could be is more than enough. Therefore, I offer it cheaper too.

The HASL version corresponds to the first prototype of the card, fully functional, but only valid for 8-bit ISA connectors, as I put the SD connector too low.

Why did you make it?

There is an Open Source version developed by Monotech-PCs. Which, in turn, is based on the schematic from XT-IDE Rev2 and Glitchworks.

For me, it is an evolution of my previous MicroXTCF project, which I have retired because I don't have any more inverted CF connectors.

What makes it special?

The version which I publish further reduces the size of the board developed by Monotech-PCs and combines most of the logic in an SPLD ATF16V8B, from which addressing of the IC 28C64B, as well I/O port of the XTSD interface, are established.

By default, the ROM addressing will be set to D000h, and the XTSD interface to I/O port 300h. If other configuration is required, please let me know at the time of ordering.

Access to the ROM can be enabled and disabled using a jumper. In the same way, write access to it can be enabled and disabled with another jumper, but it is recommended to keep it empty once it is configured.

BIOS

By default the XT-IDE BIOS comes configured for:

• XT(and higher)-compatible BIOS.
• Boot first hard drive unless user presses A for floppy.

Any of the above can be changed on purchase, or in your own time with the simple DOS utility and built-in jumpers. I recommend using the 186-compatible BIOS instead if you have an 80186 or NEC V20/V30, or higher, as the performance is better.