IDE-SD adapter question

Jonas M jm at
Sun Jun 28 00:46:39 CDT 2020

Hi Eugene,

On Fri, Jun 26, 2020 at 09:39:57PM +0000, W2HX via cctalk wrote:
> Hi all,
> However, I do get errors "sector not found" and if I A)bort I get INT 24 error.  I am trying to get windows 95 installed and this is certainly preventing that.
> In the BIOS settings I have the hard drive set as "USER" and these parameters:
> CY:[1024] HD:[16] ST:[63] LZ:[1024] WP:[0]
> These were the parameters in use while I was still using the actual hard drive.
> Question 1: Now that I am using an SD card instead of an IDE drive, what, if anything, should I be doing with these BIOS parameters?
> Question 2: The BIOS has an option to format the hard drive. Should I format the SD card using this facility?

The sector not found error might be because you formatted the CF in another
computer and created a partition larger than the BIOS supports (which looks
like 504 MiB given your CHS parameters?). It will kind of work and DOS will
report the full partition size but once you start writing over 504 MiB it
will wrap around and destroy the data.

>From "Enhanced IDE/Fast-ATA/ATA-2 FAQ" (

 "6.7.  I have no fancy EBIOS, but I have an 1GB partition and it works.

  Some try to work around the 504MB / 1024 cylinders issue by making a
  large partition using a friend's computer, Linux' fdisk, or something
  else. They use it for a day or two, conclude that it works, then post
  a triumphant article claiming that they found the Solution To
  Everyone's Problems[TM].

  It will work... for precisely 1024 cylinders. The very moment the OS
  or anything else attempts to write something to cylinder 1025 through
  int13 calls, the write wraps around to cylinder 0. This cylinder
  happens to hold some of the most important data structures on the
  disk: the Master Boot Record, partition table, both FAT copies and the
  root directory of the first partition."

I had the same thing happen to me the other day with a nice 2 GiB DOS
partition installed on a more modern computer and then moved to a 486.
Started transfering files to it and whoops the whole system gone. :-)


More information about the cctalk mailing list