[Simh] smallest pdp-11 that can run TECO and sockets(*)?

[Davis Johnson]

I would have to concur. I have a physical 11/05. The 11/05 (same CPU as 
the 11/10) and it is nowhere near as capable as an 11/03. For a while 
there DEC had a tendency to release two new machines at a time. One 
would out perform the previous flagship processor, probably not costing 
too much more. The other would be comparable with the previous flagship 
processor but at a lower cost. The 11/05 was the similar capability 
lower cost follow on to the 11/20.

Comparing the 11/05 is slower than the 11/03 and lacking a bunch of 
useful instructions. The 11/05 is totally devoid of any memory 
management - 64K address space is all you get.

You could not configure 64K, of course because of the reserved address 
space. Mine has 32K, which I suppose is a typical large configuration. 
Core memory was expensive. I suppose one could have added a 16K board 
and had 48K but justifying the expense would have been difficult.

On 7/7/2012 3:14 AM, Göran Åhling wrote:
> Well, I'd used the word "Weakest" to describe this aspect of a 
> computer...
>
> Without reading any PDP-11 architecture handbook (today), I'd like to 
> claim the initial design, the 11/20, to have the weakest architecture 
> within the PDP-11 family, it was released in 1970.
>
> Just as all (almost) PDP:s the customer would order a CPU, and 
> separately order as much or little of memory that was regarded 
> "neccesary" for every task... 11/20 had a max. of 56 kB (28 kW), as 
> the design has 16 bits of adressing (=64 kB), but 8 kB are reserved 
> for I/O devices.
>
> Exactely how little memory that would be enough to run an OS, Teco and 
> an async port, I can't judge, but running an emulator, like SIMH, 
> would alow for testing of this. The 11/20 was sold along with core 
> memory, so a fair core memory card size for the minimum system would 
> be elegant...
>
> The instruction set of a PDP-11 was slightly extended with EIS for 
> modells comming just a few years later,  as several options (floating 
> point support, commersial calculations support,  memory management for 
> 18 or 22 bits of address-space...)
>
> But, as Johnny says, the LSI-11, aka PDP11-03, beeing the first 
> LSI-design from DEC, released in 1975 with the new LSI-bus (aka Q-bus) 
> is always remembered as the slowest PDP of all times, even though the 
> architecture might be slightly improved over 11/20!
>
> If you would like a running real physical system, the 11/03 would by 
> far be the easier to get hold of, get running, and keep running. The 
> 11/20 would typically need 2 pcs of 19" wide, 72" high racks... For 
> emulation, this is however not an issue!
>
> /Göran
>
> On 2012-07-06 21:04, Richard wrote:
>> When I say "small", I'm referring to computational capacity, not
>> physical dimensions.
>
>
> _______________________________________________
> Simh mailing list
> Simh at trailing-edge.com
> http://mailman.trailing-edge.com/mailman/listinfo/simh
>
>
>