[HECnet] RSX or RSTS

[Johnny Billquist]

On 2020-03-21 16:19, Robert Armstrong wrote:
>> Johnny Billquist <bqt at softjar.se> wrote:
>> I think the 11/53 commonly ran at 15 MHz, while the 11/73 could be found
>> with 18 MHz. But otherwise yes, same basic system, really.
>> Not a speed demon. Upgrading to an 11/83 does make a noticeable difference.
> 
>    The big win for the 11/83 was the PMI bus, not the clock speed.

Right. I didn't even say anything about clock speeds of the 11/83.

>  That's entirely different hardware, though, and not much I can do about that.  PMI memory wouldn't be a problem in the BA123, but I don't believe there was ever an 11/83 board made with S-box handles.  Actually, I think the 11/53 and 53+ were the only S-Box PDP-11s made (at least they're the only ones I remember).

Hum? The BA123 takes plain ordinary Qbus cards, unless I totally 
mistaken. The S-box style came with the BA213. And I didn't even know 
that the 11/53 came with those. I thought it was possibly just the 
special variant for the DECserver 550 (or whatever it was called) which 
is (I guess) sortof like an 11/53, not not truly. But I guess you could 
just change boot proms, and possibly that would be enough...

The hardware differences between the 11/73 and 11/83 is purely a 
question of different memory. PMI, as you said. And the PMI memories can 
actually also be used as normal Qbus memories. So, up/downgrading 
between 11/73 and 11/83 becomes just a question of moving the boards around.

>    The M8190-AB (I think) 11/73 board was 15MHz and the M8190-AE 11/73 was 18MHz.  And you're right - the 11/53 was 15MHz.  Again, I don't think DEC ever made a 18Mhz 11/53.

Right. The 11/53 was always at 15 MHz. 11/73 and 11/83 can be the exact 
same CPU boards. The system tells the difference based on what type of 
memory is plugged in. That said, there were several revisions of the CPU 
board, some running at 15 MHz, some at 18 MHz. Some could use the FPA, 
some could not.

11/53 is actually M7554, while 11/73 and 11/83 is M8190, which existed 
in AB, AC, AD and AE variants (as well as one with no suffix).

   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