Thank you so much for your reply and for the tool. I’ll try that.
Eventually I want to try to replace the xtide rom with multy flippy bios extension, whicch is also 8k.

Thanks for this OP. Allowed me to easily boot a HDD on my 286 TA P35 (AKA Olivetti PCS 286), which has a proprietary Olivetti BIOS that limits HDDs to just 2 specific models.

Thank you BurnedPinguin for this,
I also have an old Olivetti like giantenemycat,and I tried several times to upgrade the preinstalled 40mb hd with a CF card or another hard drive to the max supported by bios (100mb) , no matter the combination the end result (I could use the pc for a while, and suddenly...) was some nasty "unrecoverable memory error" that the only way to fix it was to remove some memory sticks , reboot and put them again. Now a 256mb CF is set up as primary and no errors whatsoever.

Tested on OLIVETTI M250 , 256MB CF: OK.

Only just found about this project - what a great idea.

Haven't used it yet, but I can think of several past machines where it would have been useful...

Thanks

This is so useful that the thread should always on the first page.

With the XTide bios I found a hidden feature of my Olivetti M250.
The M250 in its specs only supports one hard disk drive, the case has only space for one, the motherboard has only one ide connector. and the bios only allow you to set up 1 hard disk.
I plugged a dual CF to ide adapter to the motherboard and let it boot with XUBDisk and... now 2 hard drives are detected. More testing is needed but I could partition the disks , format them and write a small txt file as a test.

To the OP: Is it possible to build a version in which if I choose to boot from A , it doesn't switch to C if there is no disk in the floppy drive? (useful when you can't swap the floppy disks in time, useful if you need to use you drive C but booting from floppy for testing , installing a OS or something else)

MarmotaArmy wrote on 2026-03-11, 14:50:

To the OP: Is it possible to build a version in which if I choose to boot from A , it doesn't switch to C if there is no disk in the floppy drive? (useful when you can't swap the floppy disks in time, useful if you need to use you drive C but booting from floppy for testing , installing a

This would likely require being added into the XT-IDE BIOS itself, not much I can do there. What you can try is pressing pause/break as soon as the XT-IDE BIOS appears, and then swapping your floppy disk in. You can then resume the system by pressing ctrl+pause, and select booting from a floppy. The fact is, by the point the XT-IDE BIOS appears, it is already loaded into memory and my disk is no longer needed. this might work.

'Bios hides things from me' can sometimes be worked around by setting cmos parameters with generic tools, like gsetup.

I have an athlon board, who's baked on setup program refuses to let me set a second floppy, or 5.25" type, for instance.

If I set it with gsetup, however, it works fine.

Similar may be the case with your olivetti.

Assuming you dont need the XUB for LBA support or something, it's a thing to look into.