If you have later Rev KA650 firmware you can try burning it into the EPROMs 
and running it. To be completely correct you also have to apply any ECO's 
that are required but finding those may be a bit more difficult. I had a 
KA655 that when you typed HELP to the chevron prompt it typed:

         **** ALPHA BUILD DO NOT DISTRIBUTE OUTSIDE DIGITAL ***

before it gave a fairly limited help menu. It had some interesting tests 
too for testing things like memory timing. (no I don't have that KA655 any 
more its in another collectors hands)


At 02:12 PM 12/10/02 -0500, Robertdkeys@aol.com wrote:
>On a lark, while putting together a KA650 based
>machine, I loaded an old Ultrix, and got an error
>message, "<<< KA650 PROCESSOR OUT OF REV.  Contact
>your DEC service rep for a replacement.>>>"
>
>The rev gave out two numbers 3, and 18.  Another board I
>have did not generate the message and had rev numbers of
>something like 5 and 50.
>
>I will assume that DEC service reps have gone the
>way of the dodo bird.  But, does anyone know what
>that message really means?  The processor seems
>to run OK on Ultrix or NetBSD, otherwise.  should
>I be wary of it?
>
>Should I be looking for another KA650?
>
>Thanks
>
>Bob