AS/400 9404 and TWINAX questions...

[Tony Duell]

> Good news: You could even make an Ethernet/Twinax single jack, if you're 
> not running faster than 100Mbps ethernet, as they run 1/2 & 3/6 for their 
> pairs -- just use 4/5 for twinax.
> 
> Bad news: *Most* pre-built cables don't follow the standard as to where the 
> twisted pairs should be - most just go 1/2 - 3/4 - 5/6 - 7/8 - and that's 
> bad for both Ethernet & twinax. You'll wanna punch down and/or build your 
> own cables if you're going to do this.

What?!?!?

I've made the odd 10baseT patch lead, and I was always careful to get 1/2 
as a pair and 3/6 as another pair (I think the other 2 pairs were 4/5 and 
7/8, but it;s been a long time..) Fiddling the wires into the RJ45 was a 
pain, but I assumed it was necessary....

And you're telling me commercial cables get it wrong. I knew there was a 
good reason to avoid them [1], the time in making up a cable is much less 
than the time to sort out network problems later

[1] Other horrors include the IEC mains cable with L/N swaps, one I saw 
with N/E swap(!), the null modem adapter which couldn't have worked with 
any normal pair of RS232 devices (4 strapped to 5 at each end _and_ those 
linkled across the adapter, that will short 2 outputs together...), an 
RS232 cable that used the cable screen (shield) as one of the handshake 
lines (!), and so on... 

-tony