It's possible 'to an extent'.

You can make a .vmdk that points at a physical block device, then tell virtualbox to treat that as the hard disk of the vm. This is not a normal configuration, and the instructions to do it are not user friendly, but it's doable.

https://superuser.com/questions/495025/use-ph … -in-virtual-box

There will be problems if the vintage machine does not speak LBA, however.

Virtualbox will present it as LBA, unless the .vmdk file says to present it as CHS.

If your vintage machine only speaks CHS, you need to detect the drive on the vintage machine, WRITE DOWN what the vintage machine's CHS reported geometry is, then make the raw device .vmdk file match.

(Useful reference)
https://www.forensicxlab.com/blog/vmdk

You'll need to make sure the .vmdk descriptor file uses the same geometry as that reported by your vintage machine's bios. The above reference will help immeasurably.

Virtualbox 'should' (in a perfect world) then create correct partitions using emulated dos fdisk and company.

thanks, i thought it was going to be easy but at the end it is not that easy.

maybe it is just better to install the sintechi adapter on the old pc using dos boot discs and also EZ-Drive 9.06W

at the end i would end up having multiple 2GB partitions on the SD card.

after doing all that, what happens if i insert the sd card on a newer machine to copy data FROM the SD card and TO the SD card?
Any risks of data being corrupt if i start pasting data to the fat16 sd card partitions?

Windows always wants to write bullshit to the mbr.

Not advisable for the boot volume.

If you have functional boot floppies, yes, guaranteed better in every way.

Trying to ham together virtualbox to create a bootable flash hard disk, is an exercise for 'I have a vintage computer, its floppy drive does not work. I have no way to make it work. I dont have a gotek, halp.' Type situations.

It's doable. But it's not easy, nor fun.