XBR2D96D@DDATHD21.BITNET (Knobi der Rechnerschrat) (12/23/89)
Hallo, in one reply to the thin-ethernet question, raised some days ago, somebody from SGI wrote that for the PI and the 3100 SQE(heartbeat) should be turned off. Can you please give a bit more information about that? What are the consequences when SQE is on for the mentioned machines (especially the 3100's)? A Merry Christmas and (if this should be my last message for this year) A Happy New Year 1990 to everyone on this list Martin Knoblauch
jweldon@renegade.sgi.com (Jack Weldon) (12/27/89)
In article <8912230716.aa07332@SMOKE.BRL.MIL> XBR2D96D@DDATHD21.BITNET (Knobi der Rechnerschrat) writes: > Can you please give a bit more information about that? What are the >consequences when SQE is on (especially the 3100's)? > At the physical layer, the only question is "heartbeat" or not. Ethernet version 1.0 has no heartbeat. Ethernet version 2.0 has heartbeat. IEEE 802.3 has heartbeat. The other differences at the physical layer are minor. The heartbeat is only between the controller board and the transceiver or multiplexer box. The ethernet cable "knows" nothing about heartbeat. The idea behind heartbeat it is to make sure the collision line on the transceiver cable is connected up. To quote the cabletron systems st500 manual, "at the end of each transmission by the transceiver, it must send a short burst of 10MHz waveform on the collision lead to permit the controller to check proper operation of the collision signal path. There is no collision test signal when just receiving." So everything is fine at this layer as long as the controller and tranceiver agree on heartbeat. What this means is that you can use either SQE, or no SQE--what matters is that your transceiver and your Ethernet controller agree that it is on or off. The 3000's Ethernet boards were shipped with SQE off, but can be modified to use SQE by your local field engineer, as necessary. I see no reason to do this unless your particular type of transceiver supports ONLY SQE (rare, but I have seen them...) >A Merry Christmas and A Happy New Year 1990 >Martin Knoblauch Thanks--You Too!! Jack Weldon SGI Product Support