3Com 3C905x PXE Boot ROMs

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Chip IDs

3Com 3C905B
3Com 3C905C

Compatible Flash ROM chips

Atmel AT29C512 (64 KB) (source: 3c90x.txt in Netboot CVS)
Atmel AT29C010 (128 KB) (source: 3c90x.txt in Netboot CVS)
Atmel AT29C512 (64 KB) (source: various mailing list posts)
Atmel AT49BV512 (64 KB) (soldered onto the TX-M NIC)

Flashing using 3Com's own utilities (look for util430.exe) doesn't seem to work with blank Flash ROMs.

Flashing using bromutil/cromutil

Using bromutil / cromutil from the Etherboot distribution you can flash arbitrary .bin images into 3C905B / 3C905C NICs using the Flash ROM chips mentioned above.

However there is no known method so far to generate a .bin image out of the files supplied by 3Com. Therefore you will need a 3C905B or 3C905C card with an already working Boot Agent.

bromutil / cromutil must be compiled and linked statically on a Linux workstation.
On the target system, boot a Linux rescue system (e.g. from the SuSE Linux CDs/DVD), set up the network with ifconfig and copy over the compiled utilities and the .bin image.
Determine the I/O address of the target NIC using lspci -v. As the output is most probably numeric and not in text form, watch for characteristics such as the Vendor ID, the capabilities or compare the listed interrupts with /proc/interrupts.
Depending on whether the target NIC employs a 3C905B or a 3C905C, you need to use either bromutil or cromutil:
- bromutil <I/O address> read >backup.bin saves the current ROM's contents.
- bromutil <I/O address> prog <bootrom.bin programs the contents of the file "bootrom.bin" into the flash ROM.

The Boot-ROM probably won't work immediately:

mbacfg.exe displays "No installed MBAs".
romtype.exe and romscan.exe don't detect "Bootware" also.
3c90xcfg.exe however says that the "Boot ROM is enabled".

Don't worry: the trick is that you can now call 3Com's own mbaflash.exe as it now recognizes the image present. Just ignore the version prompt ("v4.30 is already programmed") and you'll get a working boot ROM!

For this reason it also doesn't matter whether you save the existing image of a 3C905B or 3C905C-based NIC: just flash it into the target NIC's ROM. The 3C905C image won't work on a 3C905B-based NIC, of course, but just call mbaflash.exe -- it will program the correct image!

This page last changed:
December 03, 2004