> What failure does "?6" indicate?
> 
> Are you _sure_ the KA630 is supposed to work with three boards of RAM?

I don't know nearly as much about these things as other 
people on this list, but I do have a KA630 (in a BA123-A),  
and perhaps more importantly I have an original manual.
    :-)

The KA630-A has 1MB of RAM onboard and supports two 
MS630 memory modules.  It also has 64K of boot/diag ROM.
One CPU and two memory modules are supported in the first 
four slots because the C and D rows (bottom two) in those slots 
have a separate local memory interconnect (no mention why 
there are 4 slots to support a maximum of 3 cards...)  
Backplane Grant Continuity supports the top half of slots 
1-4, then 5-top, 5-bottom, 6-bottom, 6-top, 7-top, ect.

According to my manual there are three memory card versions:
M7607-AA  - 1MB
M7608-AA  - 2MB
M7608-BA  - 4MB
but I have two 8MB cards that are an after-market part 
made by Camintonn, part number CMX-830.  A quick search 
using Google even turned up a few for sale... that's probably 
your best bet.

BTW: with two 8MB cards installed the 1MB of RAM on the 
CPU gets disabled for so we don't exceed our 24-bit RAM 
address limit.

LED Status 6 means there was a failure during RAM memory 
address tests.  Here's the full list I typed up a while back:
http://www.anderbergfamily.net/ant/vax/rom_codes.html

I also just noticed that the manuals are online:
http://www.computer.museum.uq.edu.au/pdf/

Hope this helps...

Cheers,
anthony