22 Nov
2000
22 Nov
'00
3:14 a.m.
For older (classic) computers, the bus bandwidth
won't support 100Mbps
ethernet, so you have to go with one of the 10Mbps standards (I'll ignore
the original 3Mbps.. :-)).
I've only found one place where it's a problem so far, with an NE2000 card
in a slow XT compatible the data rate (even at 10 Mbps) was too high for it Of course another issue is that some of these machines
have built-in
ethernet interfaces (PERQs do, for example), and there's no way of adding
a 100Mbps card to them.
If you've got 10base2 nothing stops you from connecting it to a 100baseT
network through a repeating hub or switch. There's no need to cripple the
fast machines to support the old machines.
Or because older, larger, hardware is often easier to
maintain. Put it
this way, the DELNI (8 port AUI 'hub') is a lot easier to repair than
most of the 10baseT hubs I've seen. The DELNI is mostly 10K ECL. The
10baseT hub uses a single AMD chip that while standard (I have the
datasheet somewhere), is not easy to get as a 1-off.
But at $80 a new 100 Mbp hub doesn't break the bank. (I also have never had
a hub or switch fail. Except at work a cheap 100 Mbps switch that we were
pumping a continuous 40 Mbps through was getting intermittent failures.
We replaced it with a better one and put the old one on a lower traffic line,
no problems since.)
My guess is that my switches will be replaced by gigabit equivalents before
they fail. My hubs will probably be replaced from surplus stores as people
upgrade their hubs to gigbit.
Another
general complaint is that 10BaseT to 10Base2 media converters are
too damn expensive. You can't swing a live cat without hitting a coax
The media converter has to be a repeater IIRC, and has to correctly
handle collisions on both sides. That makes it more complex than a simple
transceiver. And I guess they're less used than transceivers so there's
less 'economy of scale'.