Ethernet Interface
One of my goals was to attach my PDP-11 to the Internet. The most economical route was to outfit it with a DEC M7504, DEQNA Ethernet interface. The interface has a 10 Mbps link speed and supports block mode DMA transfers.
The DEQNA seems to have had a problem locking up under heavy loads, so the 2.11BSD device driver was written to address this. The driver maintains a watchdog timer, so if the board locks up, the timer will expire, and the driver will be notified that it needs to restart the board. DEC eventually stopped supporting the DEQNA and replaced with the DELQA.
The DEQNA includes onboard diagnostic and boot ROMs that allow the system to be booted from this interface, using a couple different DEC protocols. The MVX11-B2 PROMs in my system do not support this board and I really have no need for these features.
My DEQNA is shown below.
The DEQNA and DELQA both require a cable to bring the interface out to a 15-pin AUI connector. I fitted a Cisco BL-50R 10Base-T transceiver to the AUI port of my cable, so I could connect it to the network. I chose this transceiver, due to past experience with it, and its extensive number of diagnostic LEDs. The cable and transceiver are shown below.
References
- DEQNA Ethernet User's Guide, 1st Edition, August 1984 (EK-DEQNA-UG-001)
