[Info-vax] booting vaxstation off alpha

[Johnny Billquist]

On 2013-02-12 08:48, Hans Vlems wrote:
> On 12 feb, 01:31, Johnny Billquist <b... at softjar.se> wrote:
>> On 2013-02-11 13:44, Stephen Hoffman wrote:
>>
>>
>>
>>
>>
>>> On 2013-02-11 07:54:11 +0000, Hans Vlems said:
>>
>>>> DECnet over DSSI works fine, provided you get the incantations right.
>>>> All I tried was CTERM and FAL and both worked as expected (reliable
>>>> albeit slow).
>>>> Another example of an undocumented, unsupported feature that works
>>>> alright.
>>
>>> Not that there is even a remote chance of seeing DSSI gear around, nor
>>> any likelihood of IP over FC nor connections, but...
>>
>>> If you ran any tests[1] with that, how well does that "albeit slow"
>>> connection perform as compared with slow Ethernet?  CI wasn't known for
>>> its network performance, as compared with DECnet over even then-current
>>> 10 Mb Ethernet, and usual recommendations back then had CI at higher
>>> cost as a backup connection.  I can't see DSSI being much better in that
>>> regard.
>>
>> That sounds weird. Do you know why?
>> I mean, CI was after all two redundant full duplex 70 Mbit/s channels,
>> compared to the half-duplex 10Mbit/s ethernet. Not to mention the fact
>> that the MTU of CI is much larger.
>>
>>          Johnny
>>
>> --
>> Johnny Billquist                  || "I'm on a bus
>>                                     ||  on a psychedelic trip
>> email: b... at softjar.se             ||  Reading murder books
>> pdp is alive!                     ||  tryin' to stay hip" - B. Idol
>
> Yes, I know what you mean Johnny. I don't think the CI was full duplex
> though.

Oh, it is. Since you have two channels, you can both transmit and 
receive at the same time. That is, by definition, full duplex.

> But it clocked a lot faster than ethernet. The cables BTW were
> physically remarkably similar,
> other than the colour. Won't say much for the electrical
> characteristics of the two of course.
> The CI bus was a lot more restricted in length than a 10BASE5 cable
> which probably
> explains the higher speed.

Possibly. I guess several factors played into it.

> The DECnet driver for the CI bus (CNDRIVER) may have something to do
> with the speed.
> Perhaps DECnet slowed down the regular CI traffic too much so its use
> was discouraged?
> Anyway, speed wasn't a designfactor. Within the cluster all disks were
> visible via the CI so
> why use DECnet in the first place. Any other disk lived behind a host
> on ethernet or another
> DECnet link.

Right.

	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