I think that this is a problem only with chip NIC RTL8139D on coreboot because:
- many other floppy works without a problem on coreboot/seabios - BOOT-PROM3 floppy disk image is not damage - BOOT-PROM3 floppy disk is also not damage - tested other floppy disk with BOOT-PROM3 and also working on vendor bios but not in coreboot - BOOT-PROM3 floppy & disk work OK on vendor bios on RTL8139D - BOOT-PROM1 floppy disk work ok with other NIC ISA 3com on coreboot - I was timeout problem with my NIC RTL8139D on iPXE: http://forum.ipxe.org/showthread.php?tid=3671 solved -> http://forum.ipxe.org/showthread.php?tid=3671&pid=9081#pid9081
but not excluded, however, that this may be a problem seabios
Regarding seabios it seems to me that the floppy drive sounds are different when working in coreboot / seabios than when working in the BIOS vendor. I noticed that sometimes after select Floppy from menu SeaBIOS, have info that Floppy drive not found while try boot from BOOT-PROM3 disk. I need power down PC then power ON and now floppy found.
Is another payload supports a floppy drive for test?