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Missing Operatin System error on UM386 Board with 256MB CF IDE

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First post, by p6889k

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I have Elitegroup UM 386 board, CF-IDE adapter and Sandisk ultra 256MB CF card. I configured BIOS with correct CHS settings. I then successfully installed MS-DOS 6.22 from floppy drive. Upon reboot I get "Missing operating system" message. If I boot from floppy, I can access C: drive just fine and read files from it. I tried FDISK/MBR from DOS6 floppy and also Win98 floppy, it didn't help. I also tried Card Tricks utility to set CHDK Autorun to ON, didn't help.

When I take the same card with the same CF-IDE adapter and use it on my Pentium 4 board, it successfully boots to DOS.

I also tried Transcend 133X 8GB CF card, configured BIOS with correct CHS, but DOS would not install on it on this board. Is there a drive size limit (not partition limit) on these older boards?

What else can I try?

Sinclair ZX Spectrum 48k, 48k+, 128k, +2
Amiga 1200, 68030/40mhz
386DX/33, ET4000, SBPro2, MT32
Dual PPro/200, Millennium II, Voodoo 2, AWE32, SC-55
etc.

Reply 1 of 3, by p6889k

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So I got the Transcend 8GB card working. I used Win98 bootdisk, applied FDISK/MBR, created a primary partition and set it as active. After that DOS installed without problems and system booted. The only problem is while BIOS can be configured for the 8GB through CHS, DOS sees the disk only as 504MB.

Still can't get it to work with the 256MB card though.

Sinclair ZX Spectrum 48k, 48k+, 128k, +2
Amiga 1200, 68030/40mhz
386DX/33, ET4000, SBPro2, MT32
Dual PPro/200, Millennium II, Voodoo 2, AWE32, SC-55
etc.

Reply 2 of 3, by Horun

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Yes there is a drive size limit in older BIOS and also versions of DOS. DOS from v4 thru 6.22 has a 2GB partition limit. Most BIOS of the 286 and 386 era have a max of 1024 cylinders, 16 heads, 63 sectors/track which leads to a max of 528Mb (504Mb). The way around that is a drive overlay program (Disk Manager, etc) or a BIOS upgrade that includes LBA or support for more cylinders. Your 256Mb CF may have an issue not related to BIOS but to how it was initialized and formatted from factory, making what would be considered the boot sector under DOS not proper or avaliable so "sys'ing" the CF does not work as it would with other drives on an older machine.
Added: did you totally wipe (remove redo partitions, reformat) the Sandisk 256 ?

Hate posting a reply and then have to edit it because it made no sense 😁 First computer was an IBM 3270 workstation with CGA monitor. Stuff: https://archive.org/details/@horun

Reply 3 of 3, by jaZz_KCS

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1) Drive size limit of the BIOS (can be overruled with the help of Overlay software a la EZ-Drive)
2) CF cards need to be set to boot-mode in order to be albe to boot OSes like MS-DOS directly from it. --> Industrial cards usually arrive in the other mode.

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