The original partitioning could use different geometry from your BIOS. Dos uses CHS anyway, not LBA, and the way the BIOS maps LBA to CHS may differ what from what kind of partition table the card manufacturer thought it would be nice to use as CHS parameters.
- I extended my tests to five cards : 16mb, 256mb, 2gb (no-name), 2gb (Sandisk) and 4gb.
- I have tried formatting the cards from my main PC (via USB adapter) and directly in the retro-PC (both with the DOS install, and independently with a boot disk).
- I have watched this gentlemen's video https://www.youtube.com/watch?v=G26cRjrt5Mg, who seemingly had the exact same problem as I did.
- I have stopped using auto-detection in the bios for the IDE hard drive (which often miscalculated the Cylinder, Head, etc.) and am entering specific values.
- The specific values make the hard drive detected and recognized every time (that got rid of the 'DISK BOOT FAILURE' error).
- As a result, the disk uses CHS now, for all the five cards.
- 16mb still not recognized by the adapter. 256mb and 2gb cards are detected. 4gb gives problems with FDISK because it's too large apparently.
Can think of a couple of things, reformat card with SDformatter to ensure it's got a standard format.
is your disk fat32 or fat16 ?
- The cards have been formatted as FAT16 both on my main PC and with a DOS boot disk on the retro machine.
- I have not tested SDformatter yet, but will try soon.
from a boot disk, and after having installed MS-DOS and all of that try:
- This worked, only once, on the 256mb card. But DOS didn't like it and there were apparently unknown commands in the CONFIG.SYS that were skipped.
- My boot disk was created with the same version of DOS that I'm installing, so I don't know how/why commands in CONFIG.SYS could be unknown or unrecognized.
- When I did try to reproduce this result a second time (install DOS, SYS C:, FDISK /MBR) it didn't work and gives me an 'Operating system not found'.
I have a similar problem with an sd to compact flash converter and then using the compact flash as IDE. I can access it and read/write files to it but can't seem to boot from it. Wonder if sd cards have some weird write protection on the first sector. Haven't checked yet if there's an actual valid bootsector there.
They don't have a weird write protection, but when fiddling with anything that may touch the partition table, it is possible that the card ends up being looking like a floppy (no master boot sector like fixed hard drives, starts with just partition boot sector like removable floppies).
- I have the same issue as Harekiet. If I boot from the SD Card, it says 'Operating system not found'.
- It gives 'Operating system not found' even if MS-DOS is installed on the disk. And even after a SYS C: + FDISK /MBR.
- If I boot from a boot disk, then access (write, read) files on the SD Card, it works flawlessly, as a second drive.
- There seems to be an issue with the MBR on SD cards... It gets written, but does not seem to hold the changes. At least not consistently.
- When using SCANDISK on the drive, it tells me that the MBR and MBR safety copy are not identical, which reinforces my belief that MBR on SD Card doesn't work as intended.
Well that's it for now. Will continue testing stuff then report back.