thank you for your explantion concerning boot modes and emmc flashing with rpiboot.
the problem of the failing cm3 netboot on the gumstix carrier is still unsolved:
after preparing the emmc on a cmio i can plug a cm3 on the gumstix carrier, boot from emmc and access
the cm3 without any problems on the network (ssh, sshd, etc).
Bus 001 Device 003: ID 0424:ec00 Standard Microsystems Corp. SMSC9512/9514 Fast Ethernet Adapter
Bus 001 Device 002: ID 0424:9512 Standard Microsystems Corp. SMC9512/9514 USB Hub
Bus 001 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub
eth0: flags=4163<UP,BROADCAST,RUNNING,MULTICAST> mtu 1500
inet 10.99.3.6 netmask 255.255.128.0 broadcast 10.99.127.255
inet6 fe80::18f6:2409:6fe6:d88c prefixlen 64 scopeid 0x20<link>
ether 00:15:c9:29:34:91 txqueuelen 1000 (Ethernet)
RX packets 9256 bytes 591955 (578.0 KiB)
RX errors 0 dropped 0 overruns 0 frame 0
TX packets 478 bytes 95182 (92.9 KiB)
TX errors 0 dropped 0 overruns 0 carrier 0 collisions 0
this implied for me, that the gumstix carrier ( https://store.gumstix.com/gumstix-pi-co ... ernet.html
shall be suited for network boot. but as posted before, i don't get any dhcp request (or other net traffic) from the cm3,
once i empty /boot completely or leave only bootcode.bin.
i have chosen the gumstix, since it seems the only cm3 carrier with a suitable lan9512 available. are there others?
the idea to circumvent the missing ethernet on the cmio with a usb to ethernet cable adapter failed, because i found
no one with lan9512/14.
what shall i do to check that the LAN_RUN pin is enabled correctly. i thought checking the lan working with emmc boot
shall be sufficient.
digging now even deeper in the raspberry forums, i found no post indicating a carrier board for the cm3, where a successfull
dhcp boot worked.
thank you again and best regards