I've been trying for days to set up a compact flash in my 286-12 to no avail. I am reasonably familiar with the process as I have compact flash cards working in my Socket 7 machine and in myTurbo XT (the latter with the help of an XT-IDE).

This particular 286 machine however has a Phoenix 80286 ROM BIOS PLUS Version 3.10.22, and unfortunately it doesn't allow for "User Type" in the Hard Disk geometry - it only allows for selection of one of the 47 types of predefined hard disks. The machine came with an old Seagate ST-157 45mb IDE stepper which works and boots to DOS when Type 36 is selected in the setup.

I tried with 3 different IDE card readers, 2 different multi-IO ISA cards, and 2 different CF cards - a Sandisk Ultra 512mb and a Transcend Industrial 128mb. At first I tried just putting the cards in the reader but of course it gave a "Hard disk failure" message at boot. Then I thought I would use the geometry data of some existing hard disk types from the 286 bios to Fdisk the cards accordingly in my socket 7 machine.

So I transfered the Transcend card in the Socket 7 PC, chose "Normal" instead of "LBA" in the BIOS and "User" instead of "Auto". I manually entered the data from the existing "type 41" from the 286 BIOS: 917 Cylinders, 15 Heads, 0 for Precomp (which is actually -1 in the 286 but I wasn't able to enter a negative value), 918 for Landing Zone and 17 Sectors. Which gives a size of 119mb, which is below the card actual capacity (128mb). I ran Fdisk on the card, created one primary DOS partition the formatted /S to put the sytem files on it. The Card then booted to DOS 6.22 in the socket 7 machine without a hassle.

Just to be sure, I did the exact same thing with the Sandisk card, this time choosing a different geometry that doesn't have "-1" for precomp. I chose type 34 - 965 Cylinders, 10 Heads, 0 Precomp, 965 Landing Zone; which gives a size of around 80mb. Again, the card boots to DOS in the Socket 7 PC.

When transferred to the 286 however, both cards refuse to boot, even though I configure the BIOS with the matching geometry. If I boot with a floppy, I can access the card as C:, type a DIR command which lists the contents with the correct partition size. However if I try to read anything on it, the system hangs for a few seconds and then gives some "drive C: read error" message.

What is preventing the system from accessing the CF card? Is there some kind of incompatibility, the card being too fast or something like this? Anything else I can try before giving up? If anyone else managed to successfully install a CF card in their 286, I'd love to hear about it 😵