Considering you have norton disk editor. Could you try the following.

Use diskedit to clear the first 64 sectors of the flash card while in the pentium & REBOOT and then do the fdisk, format /s, etc steps.

Let us know if it changes anything.

thanks.

edit:
and since you have diskedit you could look at both a working & non working cf layout and try to figure out how they differ.
comparing bios parameters vs partition table parameters seems a good start.

weedeewee, thanks for the answer

Tried the following:
- clearing up first 64 sectors on the pentium, all zeros
- reboot
- fdisk, format, sys c:, boot - works
- clearing up first 64 sectors on the pentium again
- transferring CF 2 IDE to 486
- still no joy, same old symptoms
- sadness 🙁

ok, I thought It could've been some misalignment issue but seems like it's more complicated.

1so you have a clean CF card in a 486
2
3then you fdisk & format /s in the 486 and get no errors but you can't boot from the CF card in the 486 nor can you do any further operations from within dos on the partitioned CF card in the 486 though diskedit in direct/raw mode does work. 
4
5additionally the CF card, while partitioned & formatted in the 486, does boot int the pentium. 

Is this summary correct?

I would swear i've seen similar issues pass by here on the forum though F me I can't find a quick solution to it.

Sounds like you may have a buggy bios that can’t handle the geometry of your CF device.

I’d try replacing your BIOS int 13h on your 486 as the next troubleshooting step. You can do that by upgrading the bios for your motherboard, adding an XTide universal bios option rom, or installing ez drive disk overlay. https://www.vogonsdrivers.com/getfile.php?fileid=1900

EZ drive might be the simplest thing to try as a diagnostic step. It will check out your device for you during the installation and warn you if it sees unexpected hardware behavior.

weedeewee wrote on 2025-05-24, 16:33:

Is this summary correct?

Yes, it is.

douglar wrote on 2025-05-25, 02:40:

I’d try replacing your BIOS int 13h on your 486 as the next troubleshooting step. You can do that by upgrading the bios for your motherboard, adding an XTide universal bios option rom, or installing ez drive disk overlay. https://www.vogonsdrivers.com/getfile.php?fileid=1900

EZ drive might be the simplest thing to try as a diagnostic step. It will check out your device for you during the installation and warn you if it sees unexpected hardware behavior.

Thank you, will try them and report back.

My advice is always have multiple models for each component. Sometimes things work out just by changing the parts. Do you have any other cards or adapters to use?

For example, only 1 model of CF adapter works on my Socket 8 motherboard. The others just wont read any cards.
Then only 2 out of 7 different CF card models works. The rest of the cards are not being identified, or hangs when being read, or crashes during W98 installation.

While on my P3B-F Slot 1 Motherboard, all CF adapters works fine, and all 7 CF card models can run W98 perfectly.