15D600BL00 INT 15 - later PS/2s - READ BOOT DEVICE ID
15D600BL01 INT 15 - later PS/2s - WRITE BOOT DEVICE ID
15D601BL00 INT 15 - later PS/2s - READ BOOT DEVICE KEY
15D601BL01 INT 15 - later PS/2s - WRITE BOOT DEVICE KEY
15D602 INT 15 - later PS/2s - QUERY BOOT REFERENCE PARTITION