This chart by Jim Rees, July 1990

Jumpers for 3Com 505 ethernet board installed in Apollo Otter series.

In this chart, 'x' represents a jumper.  '.' represents no jumper (only
shown where necessary for clarity).

This chart is not to scale and does not show the jumpers in their proper
places on the board.

BNC/DIX as needed (DIX is xcvr connecter, BNC is for thin ether)

For Mem Addr and IO Addr (port), jumper to the right is '1' and to the left
is '0'.  High numbered bits are most significant.  Append 9 zeroes to Mem
Addr and 4 to IO Addr.  In this example, the Mem Addr is CC00 and the port
is 300.  In practice, almost any Mem Addr that doesn't conflict with another
device seems to work.  I've used both CC00 and 8000 in my dn3500.  The 'LN'
command at the MD prompt will tell you what network controllers you have at
which addresses.

'EN' should be to the left (0) if you have a boot prom, to the right (1) if
you don't.

Mem Addr
13 x
14  x
15  x
16 x
17 x
18  x
19  x
EN  x

IO Addr
x  4
x  5
x  6
x  7
 x 8
 x 9

DMA  INT  INT  DMA
           x    xx
          10    6

Test
   x
On Off

   2
.  x
.  x
On 1
Config

    ROM Sel
Off x.  x.  On
    A16 A15