Re: Etherboot with 3Com 3C509

[Ken Yap <ken@nlc.net.au>]

> The 3Com card has a software programmable I/O port base address.  The
>lowest possible address is 0x210 or somewhere around there.  I was trying
>to boot a system which had a serial mux card at I/O address 0x100.  It
>would not boot.  The "probing" message would appear continuously (if
>I connected a video card).  Also, I could see activity on the first
>serial port during the probes.  I think the etherboot EPROM was looking
>for the NIC at the wrong place.  I had to change the serial mux card
>I/O address to 0x500 to get the system booted.  I tried a few different
>NIC I/O addresses but none of them worked.  It appears that the etherboot
>code is looking for the NIC at invalid I/O addresses.  Also, when it
>finds the (16650V2) UART, it gets unhappy and stops looking further.
>
> I did not investigate this problem.  I was satisfied with my work-around
>of changing the serial mux card I/O address.  You (or somebody else) may
>want to look into this, or at least mention the issue in the etherboot
>documentation.

What is happening is that the 3c509's default identification port is
at 0x100.  That's why a 3c509 driver doesn't need to be told where the IO
port is, it can query the card. A specific sequence is used to activate
the ID port, for details see the code.  I think there is a way to try
other ports 0x110 and upwards if 0x100 is taken, but I never looked into
this because I never had any other device at 0x100.

[Cc'ed to netboot for info.]
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