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I am attempting to use a SD Card-to-IDE adapter to replace a failed HDD in an ancient DOS laptop. However I am having trouble due to not knowing what settings I should use in the BIOS with regard to the adapter's "disk geometry". I've inserted a 4GB SD card into the adapter (although I'm happy to only use maybe 64MB of that).

The chip on this device is an "FC1307A" but I am unable to find any datasheet for this device. It's physical interface is a standard 44 pin IDE connector for a 2.5" hard drive (of the type used circa 1990).

The fields that I need to specify in the laptop's BIOS are as follows:

  • Drive Type [98 or 99]
  • Number of Heads [1 to 16]
  • Number of Cylinders [1 to 2048]
  • Number of Sectors per Track [1 to 63]
  • Write Precompensation ["None", or 1 to 2048]
  • Landing Zone [1 to 2048]

Is there any way I can interrogate the adapter to find out what values this device uses for Heads / Cylinders / Sectors etc?

On the laptop itself I have DOS 6.22 booting from a floppy disk, but beyond that I'm open to other methods of connecting to this device (e.g. Linux or prodding at it with an oscilloscope or logic analyser).

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    I am very confused by your question since flash storage like the SD Card you are attempting to use does not have heads or cylinders. Even the concept of sectors, is significantly different, due to the firmware required to keep the device healthy when it comes to writes. What makes you think this adapter will even work? Why are you not just using a used replacement IDE HDD?
    – Ramhound
    Feb 28, 2022 at 19:27
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    Don't be confused. The laptop's BIOS cannot automatically identify the geometry of the drive. When this laptop was built hard drives did have cylinders, heads etc... The laptop's interface is forcing me to specify something! I know this adapter can work to at least SOME degree because I have had PARTIAL success in installing DOS on it. Partial success is a long way from actual success :) The problem is that the laptop needs some ideal set of geometry numbers for it to understand this adapter properly. 386SX machines are not very flexible, so I have to work with the parameters I have. Feb 28, 2022 at 19:55
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    From vogons.org/viewtopic.php?t=55861 "I've been plugging it into a system that does have auto detect and then writing down the heads/sectors/etc for each SD(or CF) card." There are a few other options in that thread as well idediag.exe and this one
    – Mokubai
    Feb 28, 2022 at 20:12
  • @Mokubai, idediag.exe looks very promising. It even measures the total capacity as 3718MB (and it is indeed a 4GB SD card). I'll investigate this more, thank you for this information. I'll be back to update this thread soon. Feb 28, 2022 at 20:38
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    @Ramhound: It doesn't have actual heads or cylinders, but as it emulates an IDE device, it still has to pretend to have them, for the purpose of old non-LBA-based commands. It's really similar to how actual HDDs still accepted CHS-based commands even though the C/H/S specified had no correspondence whatsoever to physical layout... Mar 1, 2022 at 5:54

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