RF08/RS08 emulation

Vincent Slyngstad vrs at msn.com
Thu Aug 7 00:26:08 CDT 2008

From: "Rich Alderson"
> General question for PDP-8 fans:  I've seen references to someone having
> created an RF08/RS08 replacement.  Does anyone on the list know details
> of such a project?

I have a project like that.  You can find Eagle drawings at
Look for "RF08: RF08 Replacement" in the green scrolling region.

The idea was to order an 8"x11" panel containing a controller, two 
drive pairs, and a light panel.  The "drive pairs" are implemented 
with pairs of SRAM chips, which taken together form a removable 
512Kw battery backed store.  Two such stores provide the full 1Mw 
of storage.  The 40 pin headers take BC08J cables or the equivalent, 
to connect the controller to a Posibus PDP-8.

The design is my rework of C. Morris' DF32 replacement (which I 
also now own the prototype of).

Like many of my projects, it was fun to think about the design, 
but I haven't yet made the time to actually build and debug it.


N.B.: The 74LS151's in the write-protect section need to be real 
TTL, and float their inputs high without pull-ups.  Of course, if 
you don't care about separate write-protect switches for each 32K, 
you can just hard wire the inputs to the right values :-).

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