Re: eepro100+ flashing?

[Greg Beeley <Greg.Beeley@LightSys.org>]

Marty Connor wrote:

> - A 3Com 3C905C, which I want to try the contributed in-machine flashing
> utility with. (and of course make sure current Etherboot supports it).
> (hey, do you think 3Com fixed the 8K MII Select bug in this rev??)

I've <finally> asked 3com for some information about the 3c905C; hopefully
I can be more 'intelligent' in these conversations on the mailing list 
regarding this newer card :)

For the flashing utility, I'm not sure if there is already some code in the
onboard ROM or not, so the first test would be to see if 3c90xutil can read
the ROM successfully.  But there might be garbage or blank data in the
ROM initially, I'm not sure, so the test might not be productive...  See below.

As for the 8K MII thing, I have no idea.... :)

As for the flash chip on the 3c905C, the AT49BV512 is a 64 kilobyte flash
ROM that operates at 3V (as opposed to 5V for the AT29C512 used on the 
3c905B).  

The AT49BV512 is VERY DIFFERENT from the AT29C512 in more ways than just
the voltage (BV vs. C).  Here are the differences and their implications:

1)  The AT49BV512 has a "boot block" feature that means you can program
    the 8kb boot block and then write protect it permanently.  If 3com
    has programmed that boot block and write protected it, then it is
    very possible that etherboot can't be used in a traditional manner 
    with this card, and we would need some specific 3com data to find out
    how to write an etherboot wrapper to put etherboot into the 56kb of
    non-write-protected area.  However, if the boot block feature is not
    used and 3com has not protected that area, then the chip can be used
    as a normal flash ROM without paying any attention to the 8kb/56kb
    separation.  Hopefullly I will know more about this shortly.

2)  Also very significantly, the AT49BV512 is NOT A SECTOR PROGRAMMABLE 
    DEVICE.  This has serious implications for the 3c90xutil utility, which
    waits for each sector's programming to complete before continuing on
    to the next sector.  The AT49BV512 must be programmed as a 64kb chunk,
    which will likely require modification of 3c90xutil.  And I am not sure
    how 3com designed the registers for 3c905C related to register-based
    Flash-ROM access.

Greg.

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Greg.Beeley@LightSys.org        LightSys - Redeeming Technology...
http://www.LightSys.org                    For God's Kingdom.
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