LSI-11/2 CPU with tracks cut?

Hi! I got a M7270 CPU module here from my PDP-11/03. It has the tracks to the QBus contacs BC1-BF1 (BDAL18, BDAL19, BDAL20, BDAL21) cut. I of course wondered why one would do that. In [2] I found the following hint: --- II. Restricted Compatibility Options Options in this category do not meet one or both of the requirements for use in a 22-bit system. These options are incompatible with some or all 22-bit systems. ... KD11-HA M7270 LSI-11/2 CPU (16-bit addressing only, and use of BC1,BD1, BE1,BF1 for purposes other than BDAL18-21) --- So I guess someone tried to make the CPU compatible with 18/22-bit modules? What did the M7270 use these pins for? I didn't find any manuals or schematics for the this CPU yet, only for the LSI-11. Could someone point me into the right direction? Thanks Sebastian [1] http://www.bitsavers.org/pdf/dec/pdp11/1103/EK-LSI11-TM-002.pdf [2] http://www.ibiblio.org/pub/academic/computer-science/history/pdp-11/hardwar…