Ethernet Panic (AT&T 3.2.1 + Wollongong WIN/TCP)

[Scott Wiesner]

>From article <1990Nov8.002323.10142 at intek01.uucp>, by mark at intek01.uucp (Mark McWiggins):
> We've just added a couple of new machines to our Ethernet, and apparently
> this is too much for my 386 Unix system as currently configured.  I've
> been getting regular panics like this latest one:
> 
> 	PANIC: wdintr: bad nxtpkt value=0x000000FF

This sounds like the standard 8/16 bit conflict between some VGA boards
and some network boards.  A VGA board has video memory from 0xa0000 - 0xbffff
and a BIOS starting at 0xc0000 running for 16 or 32k.  Your ethernet board
probably has a data buffer somewhere in the range of 0xc0000 - 0xcffff.  If
your VGA board is setting up the bios to run with 16 bit access, it will
force all memory in the range from 0xc0000 - 0xdffff to run with 16 bit 
access.  This will make every other byte in your 8 bit network card's 
data buffer get corrupted.

The easiest thing to try is putting the VGA card into an 8 bit slot.  Some
VGA's have switches and jumpers to set the card into 8 bit mode.  If you
have the option, the only thing you need in 8 bit mode is the VGA bios, not
the video memory.

Note that this kind of conflict can happen between any two cards, but I
believe the most common is with a VGA.  You can also have a problem if you
have a 16 bit network card and use an 8 bit VGA.  (If the VGA bios is 
referenced, you'll get garbage in every other byte.)

There's a good write-up about why this happens in the Sept 25, 1990 PC
Magazine.  "Facing the Truth About 16-bit VGA Display Adapters"

Scott Wiesner
Interactive Systems
X Development Group