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

[Göran Åhling]

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.