Re: Can you MOP boot an install kernel directly?

[Paul Koning <paulkoning%comcast.net@localhost>]

> On Aug 5, 2025, at 10:02 AM, Johnny Billquist <bqt%softjar.se@localhost> wrote:
> 
> On 2025-08-05 15:31, Paul Koning wrote:
>>> On Aug 4, 2025, at 10:25 PM, Johnny Billquist <bqt%softjar.se@localhost>wrote:
>>> 
>>> ...
>>> But think about it. Even detecting and processing the trigger requiressomething to receive and process a MOP message. And this could be for a CPU halted. How would you do that unless the controller itself understands MOP?
>> Clearly, supporting trigger requires controller support.  It's just like the later "Wake on LAN" message.  But supporting trigger just requires a pattern match; it doesn't require sending anything, much less executinga protocol state machine.
>> The next step typically is primary load, which uses a single message, so a single request/response.  Again, no real state machine.  The final stage is the secondary or system load, which transfers a sequence of messages so it requires a state machine that does sequence number handling, timeout and retry, etc.  The reason for the primary vs. later distinction isthat the ROM boot just does the primary load, so it basically is a transmit and a receive, repeated until it works.
> 
> For sure you could have it like that. But the boot roms of an M9312 could never fit anything close to a MOP implementation, so unless the controller does more, a PDP-11 back in the day would never have been able to netboot.
> 
> The controller is also (all on its own) sending out MOP messages with device information at a regular interval, all the time. Even when an OS is running and using the controller. And the controller keeps a lot of counters and stuff which can also be read out via MOP without involving the PDP-11. Those DEC ethernet controllers do way more than just basic ethernet.

True for most of the DEC Ethernet controllers, though not the QNA and CNA; for those the job of doing these things falls on the device driver.  But those functions are the "MOP Console" protocol, which is actually a different protocol type than "MOP load/dump" though both are specified in the MOP spec (and both share the DDCMP maintenance mode datalink protocol).

	paul