Comment by aquabeagle

While this article is about OpenBSD's floppy support, if you already had OpenBSD on the machine and working networking, upgrading it without any external devices is as easy as:

    ftp -o /bsd.rd https://cdn.openbsd.org/pub/OpenBSD/6.7/i386/bsd.rd

Then reboot and at the boot> prompt, just type "bsd.rd".

On 6.6 and newer, just type sysupgrade and that's it.