[Simh] MOP header specs?

[Johnny Billquist]

On 2018-02-24 17:21, Paul Koning wrote:
> 
> 
>> On Feb 23, 2018, at 8:52 PM, Johnny Billquist <bqt at softjar.se> wrote:
>>
>>
>>
>> On 2018-02-24 01:56, Paul Koning wrote:
>>>> On Feb 23, 2018, at 5:28 PM, Johnny Billquist <bqt at softjar.se> wrote:
>>>>
>>>> ...
>>>>> That's why a MOP load normally consists of asking for a program - which is the secondary loader.  It's the secondary (or tertiary) loader that knows how to unpack an image and make additional requests.
>>>>
>>>> Hum. Well, that might be, but both will be served through MOP, so it don't make much difference if it's the primary or secondary boot. They are served the same way.
>>> Almost.  A secondary loader response carries the entire secondary loader in a single message, so the bootstrap only needs to handle one message.  Tertiary and OS loads are expected to take multiple messages.
>>
>> Yes. But what difference does that make on the server side? The fact that the requested image is small enough to fit into one frame is just a detail that makes the client implementation easier.
> 
> The difference is that the server is required to answer a request for secondary loaded with a single response packet holding the entire response.  For other loads, it can deliver the data in pieces, and the size of those pieces it its choice.  For the second loader, it does not have that choice.

The MOP servers I know of don't even know about that distinction. They 
just serve the image. If it fits in one frame, it will come in one 
frame. If it don't, it won't. The server can't do more than that.

   Johnny

-- 
Johnny Billquist                  || "I'm on a bus
                                   ||  on a psychedelic trip
email: bqt at softjar.se             ||  Reading murder books
pdp is alive!                     ||  tryin' to stay hip" - B. Idol