How to enable the second serial port on old vm AT&T SVR4?

Usually one serial port is sufficient to control via minicom the old SVR4 on Qemu (I know is a very old system, is unsafe, etc..). I have set those two ports on configuration of vm serial type="pty"> But on start, only one port is enabled find /dev/ -name *tty* -print /dev/systty /dev/tty00 /dev/tty /dev/tty00s /dev/tty00h So I try to rebuild the kernel. On SVR4 to rebuild the kernel first I make the changes in the file /etc/conf/sdevice.d/asy asy Y 1 7 1 4 3f8 3ff 0 0 asy Y 1 7 1 3 2f8 2ff 0 0 the syntax is simple: asy is the driver Y enable it, 1 7 1 I don't know, 3 is the interrupt (on all my system irq 3 is used by the second serial port, 4 by the first). 3f8-3ff and 2f8-2ff are the port interval, 0 0 I don't know Then I rebuild the kernel with idbuild. After reboot, same situation. If I edit the file /etc/conf/node.d/asy asy tty00 c 0 asy term/00 c 0 asy tty00s c 0 asy tty00h c 128 asy term/00s c 0 asy term/00h c 128 asy tty01 c 1 asy term/01 c 1 asy tty01s c 1 asy tty01h c 128 asy term/01s c 1 asy term/01h c 128 and recreate the nodes idmknod -s I have this strange situation ls -ld /dev/tty* crw-rw-rw- 1 bin bin 16, 0 Dec 25 19:31 /dev/tty crw--w---- 1 myuser tty 3, 0 Mar 27 05:20 /dev/tty00 crw-rw-rw- 1 root root 3,128 Mar 27 04:26 /dev/tty00h crw-rw-rw- 1 root root 3, 0 Mar 27 04:26 /dev/tty00s crw--w---- 1 root root 3, 0 Mar 27 05:20 /dev/tty01 crw-rw-rw- 1 root root 3,128 Mar 27 04:26 /dev/tty01h crw-rw-rw- 1 root root 3, 0 Mar 27 04:26 /dev/tty01s All files use the major number 3. Why the 4 is complete ignored? What I miss? Probably a bug in the kernel or what else? On all my system the two serials are recognized, modern (Linux) and old (Sco Unix). I see with SVR4 that it cannot see any serial port (except the first) on qemu but also on 86box and bochs.