HP board id?

[J. David Bryan]

On Wednesday, May 13, 2015 at 19:40, Marc Verdiell wrote:

> ...where to get the older CTuL logic IC bus drivers (the 9956 in
> particular) besides from old boards? 

With the inclusion of a pulldown resistor to -2V, the TI SN75121 is a 
recommended replacement, per page 5-6 of the "HP 1000 M/E/F-Series 
Computers I/O Interfacing Guide" (02109-90006 September 1980).  It's an 
active part:

  http://www.ti.com/product/sn75121

                                      -- Dave