DEC VT20 boot device

[Jay Jaeger]

On 8/10/2019 1:56 PM, Paul Birkel via cctech wrote:
> The DEC VT20 terminal apparently included a PDP-11/05 with a direct mapped
> character display and was intended for text editing and typesetting.  It
> seems to have been followed by the VT21, and then VT71/VT72, all three based
> on an LSI-11 (KD11-F).  There's a real lack of documentation about these
> online, although the VT72 does have a print set.
> 
>  
> 
> Apparently the VT20 used the M792-YK as its bootstrap; the Field Guide is
> silent regarding the boot device and M792 documentation stops earlier in the
> series of variants.
> 
>  
> 
> According to the VT72 print set, it used the MRV11-VC (M9942-YC; described
> in the Field Guide as a "bootstrap/diagnostic module") for its bootstrap but
> is also silent regarding the boot device.  In interestingly, the Field Guide
> also describes a MRV11-AA (M7942-TB) as a "M7942 with VT52 emulator, VT71
> bootstrap".
> 
>  
> 
> For async. communications the VT20 used a DL11-B (M7800 (EIA)). the VT72 a
> DLV11-F (M8028).
> 
>  
> 
> Looking in a DEC "Options and Modules" listing I see VT20 bundles including
> Typeset-11 and DECset-11, and it appears that the VT20 could be configured
> with two displays & serial lines in a single 11/05.
> 
>  
> 
> So . is the boot device in these systems the remote host via the serial
> line?  What protocol would that have been?  Something native to Typeset-11
> and DECset-11?
> 
>  
> 
> paul 
> 
> 

I wonder if, maybe, it used the same protocol as the GT40, which also
had a boot-over-serial line capability.

JRJ