Still pineing for my own VMS machine

DECnet is a byte-oriented protocol over an unspecified physical medium (typically RS-232 or V.35). What may be occurring here is that the modem _is_ a plain-old-dumb (sync?) modem, but the byte protocol between the VAX and the Customer Care center in Colorado (where Remote Diagnostics folks used to reside) is a DDCMP or simplified DDCMP connection as opposed to some other proprietary method of packaging the requests and data.

Older remote diag stuff (L0006? in an 11/750) would certainly have had some odd, proprietary, possibly interactive method of communicating with Field Circus. I can imagine a human really dialling in and issuing interactive commands at an 11/750. By the time the VAX 6000 came out, they probably wanted a program doing the low-level work, so they may have rolled out a networking protocol which is not based on human readable commands and <CRLF> command seperators, and that allows for in-band error detection - all the things we like about network protocols - automatic and robust, unlike throwing commands at a console prompt. Not just dumb in the sense of a dumb terminal, but older VAX console lines tend to be resource hogs on the CPU, sometimes due to the interrupt level the UART comes in at, sometimes just due to the fact that it is a programmed-I/O device, not DMA like a DMF-32 or other "TXDRIVER" (vs "TTDRIVER") compatible serial device. It's why I was happy to put that DMB32 of yours into my 8200 - I have four console serial lines to start with: OPA0 and three others. I have been told that they exact a toll on performance to use them heavily (Kermit and the like). The normal mode for a VAX was to stick a printing terminal on OPA0 and let it spill paper on the floor all day. Who cares if a 300 bps connection gets serviced at half the max transfer rate - it's not like a _user_ is waiting for the printing to finish. For output, the OS can pace the console printing and defer it until later, giving better response for the live humans on the other ports. Contrast how long it takes for an operator message to print vs. when the OS panics - with absolutely nothing better to do that scream for help, the console speed picks up - you can hear the change in the cadence. That's how we always knew the VAX crashed - by

-ethan