>Brad Knowles writes:
>At 3:07 PM -0700 on 11/25/01, Don Yuniskis wrote:
>
>>  The Classic has 10BaseT w/AUI.  The SS1+ and SS2 have AUI.
>>  Rather than looking for two different kinds of cards, I
>>  figure *use* the RJ45 on the classic for one I/F.  Then,
>>  *add* an AUI/10Base2 NIC for the *other* I/F.  This makes
>>  the best use of the existing ports on the Classic and
>>  just requires adding at most a 10base2 xceiver (assuming the
>>  NIC doesn't have a BNC already on it!)
>
> Just because you've got multiple sockets doesn't mean you 
>actually have multiple interfaces.

Correct.  You will note that my description (above) claims
*adding* "an AUI/10Base2 NIC for the *other* I/F".  Most
NIChips are designed so that you just add another isolation
transformer and you get a second media connection on the
*same* interface.  The NIChip either automatically selects
the active connection (by looking for signal activity)
*or* allows you to "manually" select the connection to
use with an appropriate register write.

>I'm 99.99999999% certain that you 
>will have just one built-in interface on these machines, although you 
>may be lucky in terms of what sockets are provided for you to plug 

Correct.  That's why the discussion of "should I use the built-in
RJ45 (10baseT) and add a 10base2 SBUS NIC?  vs. use the built-in
AUI with a 10base2 transceiver and add a 10baseT SBUS NIC..."

>into.  Consider old 3Com 3C509-combo cards that had 10Base-5 AUI, 
>10Base2, and 10BaseT all on the same card, even though it was just 
>one interface -- you've probably got a similar situation.
>
> Solution: Use only 10BaseT interfaces, and for those machines 
>which don't have built-in 10BaseT interfaces, either use an 
>AUI/10BaseT transceiver, or buy a second NIC to use.


The problem isn't which *one* media connection to use -- rather,
how best to get one 10baseT and one 10base2 connection ON TWO
SEPARATE I/F's on the same box.

> Myself, I'm quite fond of Quad FastEthernet (QFE) cards -- four 
>10/100Base-T interfaces in a single card.  Moreover, it will have a 
>decent amount of on-board buffer space available, unlike the standard 
>built-in interfaces you will find on most machines (you may not see a 
>measurable performance hit with 10BaseT, but you will see a higher 
>CPU loading as the main processor gets interrupted a lot more to 
>handle data).


If you note in my previous comments, I don't run CAT5 between
machines -- RG58 instead (for reasons explained elsewhere).
So, having 4 RJ45's on 4 I/F's is just 3 *wasted* connections
for me  :-/

> For a router or firewall, you really, really want to have all 
>interfaces running on add-in NICs, so that you can avoid this problem.


Are you stating that the network interface on the motherboard is
implemented in an inferior manner?  I.e. no DMA, etc.?

Thx,
--don