On Wed, Jun 28, 2023 at 6:00 AM Grant Taylor via cctalk <cctalk@classiccmp.org> wrote: > > Tony's email makes me ask more questions than I have (smart alack) > answers to. Maybe ~> hopefully I can ~> will learn something.
I was being a bit of a smart alec too. The point I was making is that a bit of normal IDC ribbon cable is not electrically the correct cable for an AUI interface but it won't matter over a few inches. The correct cable is 4 twisted pairs with a overall screen (shield). One pair is thicker wires than the other 3 and is used for the power. This cable was very hard to get by the metre when I needed some about 30 years ago, and a full reel was several hundred pounds. I was lucky enough to be given a couple of metres as an 'offcut' by a gentleman who worked in network support. You probably need something like that if you're makng a 1m cable. But not for what the OP is trying to do. > > On 6/27/23 10:26 PM, Tony Duell wrote: > > For a few inches, which would be enough here I think, I've used an IDC > > DA15 plug and socket crimped onto the normal ribbon cable. Technically > > it's wrong but the reflections on that length of cable won't matter. > > Isn't 10Base<something> quite resilient? Especially at these distances? There are 2 problems with the wrong cable. Firstly will it carry the current for the power supply pins? My experience is that it will, at least for most transceivers. The second is that the characteristic impedance is wrong. It's actually not too far off but... This will cause reflections. It won't matter on a few inches as the reflections will take about a nanosecond to get back and will die out in << the bit time. It may matter on longer cables. > > Though I don't know if AUI is considered 10Base<anything> in and of > itself. Doesn't it become 10Base5 / 10Base2 / 10Base-T based on what > transceiver is on the other side of / attached to the other end of the > AUI cable? AFAK AUI is not 10baseAnything for the reason you give > > I'm assuming that MAU is meant for multiple stations to connect an AUI MAU is something like 'media access unit' and is the official name for a transceiver. Due to the fact that there had to be a certain distance between transceivers on the cable, there were things that had multiple AUI connectors to link to computers (these were normally male DA15s on the unit, so a normal transceiver cable would work) and a further AUI connector (normally a female DA15) for a transceiver onto the 'real' ethernet. DEC's DELNI is a common-ish example of such a unit, I think the printset is on bitsavers > cable into and it then connects to the ostensibly 10Base<something> > network. -- I originally read and was replying as if Chris was trying > to take the AUI port on his Pro/380 and connect it to an AUI port on a > hub / switch. My concern being that both AUI ports would be the same > gender and assuming that there are (at least) a pair of transceivers > converting each device from AUI to 10Base<something> to connect to each > other. There is no real equivalent of an 'AUI null modem cable' (should that be 'null transceiver cable'?) If you want to link 2 computer-type ports together you need the equiavelent of 2 transceivers. Probably the easiest is a pair of 10baseT transceivers and a crossover 8p8c cable If you want to link 2 transceivers together on the AUI side then that's a network bridge. Even a basc one is quite a lot of electronics. If you want it to only pass on packets for particular machines then it gets very complicated, one that I picked up last year contains a 68020 CPU _and_ a board containing a 16 bit processor made from 2900-series bitslice stuff -tony
