sek@sword (Spencer Kantor) (05/31/89)
We've recently encountered some problems with Apple Macintosh's when connected to a twisted pair ethernet LAN. We're curious whether anyone else has seen similar problems. Background: So far we've uncovered two problematic Mac II's. Each has an Apple EtherTalk card installed. The only other card installed on the Nubus is an Apple video card. Each Mac was connected to an ethernet LAN using thick transceiver cable coming off a multiport transceiver prior to being moved to their new location. Both Mac's worked flawlessly with their former network arrangement. Current Situation: We recently installed a twisted pair ethernet LAN in a new portion of our building. We're using ODS (Optical Data Systems) concentrators and transceivers. Onto this segment we moved the two Macs mentioned above, 4 other Mac II's (having an identical configuration to the 2 problematic Macs), 3 diskless Sun workstations, 1 IBM PC, and 1 Altos microcomputer. After some initial cabling problems, all other machines are working fine on the new twisted pair segement. The Problem: The network connection is made via a twisted pair transceiver. The transceiver has a DB-15 connector on one side and a RJ-45 on the other. The transceiver connects to the DB-15 connector on the EtherTalk card. Power to the transceiver is supplied by the computer.This is in contrast to the power arrangement when multiport transceivers are used. In that case power comes from an outside source - i.e. they're plugged into a 120V line. With the Macs (and other computers) that are functioning correctly, when the computer is turned on, power is supplied to the twisted pair transceiver. A red LED shows that power is received. With the two problematic Macs, no power is being received by the transceiver hence no network connection is attained. What We've Tried: To date we've swapped transceivers including trying new transceivers as well as those currently working with the other Macs. We've tried tranceivers manufactured by another company (Synoptics). We've moved the EtherTalk board to different slots on the Nubus (more on this is a moment). We've swapped EtherTalk boards. In each case the transceiver claims it's not receiving power from the Mac. We then carried the Mac to an office with a thick ethernet connection which didn't require using the twisted pair transceiver. The Mac and each EtherTalk board worked fine. Hence we concluded that we're seeing some problem with the Mac II generating the necessary power for a twisted pair ethernet transceiver to function. We were able to put a meter on the DB-15 connector of the EtherTalk card. With the Macs that are functioning correctly we detected 12v (actually slightly under but within spec). With the problematic Macs we detected 0.00v. Temporary Workaround: To get the Macs in question on-line, we're using an externally powered multiport transceiver with the twisted pair transceiver. The temporary arrangement has the twisted pair transceiver connected to the network input port of the multiport transceiver and a standard thick DB-15 cable connecting one of the output ports of the multiport to the EtherTalk card. Everything works fine particularly since the twisted pair transceiver is receiving its power from the multiport transceiver. Questions: It's obvious that no power is coming through the EtherTalk cards of the two Macs in question. Our questions regarding this are as follows: 1- Is it correct that the EtherTalk card does not generate power and that all power is coming off the Nubus? 2- Does the Apple video card require power from the Nubus as well. If so, how can we have the condition where there's no power coming through the EtherTalk card but the rest of the machine (including the video card) works fine. 3- Do you think the problem is in the power supply or elsewhere? (if so, where?) Again will a malfunctioning power supply still allow the rest of the machine to operate properly? 4- Do the positions of the cards on the Nubus have any power implications. Apple's only response so far (which we haven't tried yet) is to put the EtherTalk card before the video card on the Nubus. There was some thought that the video card may be drawing too much power preventing the EtherTalk card from receiving sufficient power. 5- In the absence of a Nubus power supply problem, what explanation(s) can account for the symptoms we're seeing? 6- Has anyone else encountered this problem, and if so, what was your resolution? Sorry this became so long, I wanted to be thorough in describing the problem. Thanks for any help/suggestions offered. Spencer Kantor Bell Communications Research bellcore!nvuxr!sek sek@sword.bellcore.com
rjk@mtung.ATT.COM (Roberto Kohler) (06/06/89)
We have had no problems connecting our Mac IIs and Mac SEs to a Twisted Pair Ethernet Network. We are using AT&T StarLAN 10 AUI Adapters and StarLAN 10 Hubs. The MAC IIs have a video board and a 3COM Ethernet board. The AUI adapter connects directly to the Ethernet board and receives its power from the computer. Unshielded twisted pair connects the AUI adapter to a StarLAN 10 Hub (multiport repeater). Roberto Kohler AT&T Bell Labs rjk@mtung.att.com