3C905B-TX Boot Prom Mapping?

Thu Mar 4 12:08:42 1999

Hi,
I am not a hardware specialist, but from a commercial bootprom maker we got the
following information concerning some revisions of the 3c905b-tx:

              - different chip set, it is us e.g. 40-0483-001 well-known,
addresses only the first
              4KB of the 64KB ROM of area. It concerns an error in the 3C905B
chip set here.
              A special format of the ROM image was made and a 3Com Patch was
applied, so
              that the full ROM area can be used.

Sorry for pidgin english translation, it was done by
http://babelfish.altavista.digital.com/

Greeting from Berlin, Germany
- Joachim Jaeckel

Oscar Stiffelman wrote:

> Hi,
>
> I am working on getting a diskless beowulf with bootp/tftp running Linux
> (Redhat for Intel).  I recently set up a diskless node using the 3c905B-TX-M
> (the MBA card).  I used an intermediate boot loader,
> http://cuiwww.unige.ch/info/pc/remote-boot/ and PXE.  I was not able to boot
> directly to the linux kernel (without using the intermediate boot loader).
>
> -- Oscar Stiffelman
>
> > -----Original Message-----
> > From: owner-linux-vortex@beowulf.gsfc.nasa.gov
> > [mailto:owner-linux-vortex@beowulf.gsfc.nasa.gov]On Behalf Of Dan Marks
> > Sent: Sunday, February 28, 1999 7:51 AM
> > To: linux-vortex@beowulf.gsfc.nasa.gov
> > Subject: 3C905B-TX Boot Prom Mapping?
> >
> >
> >
> > I am interested in using the NetBoot package to create a BOOTP/TFTP image
> > for my 3Com 3C905B-TX ethernet card.  However, it seems that the
> > "standard"
> > type ROM images do not work.  I have the version of the card that has the
> > vertical ROM socket, not the horizontal one.  What I am calling
> > the "standard"
> > ROM type is the type that maps the entire ROM contents (usually
> > 16k or 32k)
> > into the upper conventional memory area.  It appears that this version of
> > the 3C905B I have does not do this.  The 3C905B takes either a 64k or 128k
> > part (the ATMEL 29C512 or 29C010).  It seems that in order to
> > avoid mapping
> > in such a large ROM in its entirety, 3Com decided to have only the first
> > 2 kilobytes of the ROM visible in the conventional memory area.  The code
> > in this 2K copies the remaining 62K off of the ROM into
> > conventional memory
> > (I think) where it is executed and the actual boot loader code runs.
> >
> > This means that the conventional boot ROMs that can be built by
> > the NetBoot
> > package (http://www.han.de/~gero/netboot/) won't work because they expect
> > to be mapped in their entirety into conventional memory.  I do not have
> > the 3C905B-TX technical (register level type) documentation.  But if there
> > were a register on the 3Com board that controls how much of the ROM is
> > mapped into conventional memory (such as in the EEPROM), then perhaps it
> > could be set to allow the entire memory to be mapped.
> >
> > Alternatively, if the registers on the 3C905B-TX were known that controls
> > the memory mapping into extended memory of the ROM, then a similar boot
> > loader snippet could be written for the visible 2K of the 3C905B boot ROM
> > that would similarly copy the Netboot code into conventional memory and
> > allow it to function normally.
> >
> > Another snag I've found is that it seems there may be a special
> > "signature"
> > needed to make the ROM visible that I do not know.  This "signature" if it
> > existed would be above and beyond the "55AA" signature for any ROM in the
> > PC architecture, and is also not the "$Pnp" or "PCIR" signature
> > blocks that
> > are present in the ROMS for PNP and PCI cards (or perhaps it may be a
> > nonstandard version of these signature blocks).  I have attempted to build
> > a NetBoot ROM on a 29C512 part with the PCIR and $Pnp signatures that
> > signify a network bootable ROM, but the 3Com card refuses to even map it
> > at all and does not allocate any conventional memory space for
> > it.  I think
> > the 3C905B may be looking for this signature and not mapping the card at
> > all if it does not find it.  All I can really find out about the signature
> > from 3Com is that, because they have acquired a company called Lanworks
> > to write their boot roms for them, they have decided to make all of the
> > boot ROMs proprietary and the information about such a signature would not
> > be available from 3Com.  This is especially disappointing because it would
> > probably mean that future 3Com cards would require proprietary boot PROMs.
> >
> > This new ROM format is part of the 3Com "Tri-ROM" MBA ROM format (I guess
> > so named because it supports TCP/IP, Netware, and PXI), which is what
> > necessitated such a large ROM part to be used.
> >
> > So far this is what I know.  If someone knows any technical information
> > about the ROMs or their mapping registers it would be much appreciated.
> >
> > Dan Marks
> > dmarks@uiuc.edu
> >

--
Joachim Jäckel
Tel. +49 30 39103921 Mobiltel. +49 172 3923214
Fax  +49 30 39103922 mailto:Joachim.Jaeckel@jj-it.de
http://www.jj-it.de/