Qbus identification

I hope that Allison is available to determine if I am suggesting a possibility that might damage a board of the backplane. I doubt that is a possibility, but just in case, can anyone else please comment as well. A BA23 box is wired with the top 3 slots as Q/CD and the lower 5 slots as Q22 / Q22. If a backplane slot is wired as Q / CD, then that slot can hold ONLY a single board, either dual OR quad, on the left side of the slot. If a backplane slot is wired as Q/Q, then either one quad board or two dual boards are used. The order of the boards in a BA23 is: !A 1 2A 2 3A 3 4A / 4B 4 / 5 5A / 5B 7 / 6 6A / 6B 8 / 9 etc. Depending on if your PDP-11/73 uses any or none of the "B" portion of the backplane when a dual board is present, you already know if any of the backplane is Q/Q. Since you have not provided a list of the boards and the location of each board, I can not comment further. However, you can always place a dual board in an "A" slot and leave "B" portion empty. If that slot is Q/Q, then the bus grant will be broken and any boards beyond that location in the chain will not interrupt. If I have not explained the situation carefully enough, please ask more questions. Do you already have the M8190-AE and the PMI memory boards? If you do, then you may want to compare the speed difference. When I performed a similar benchmark under RT-11, I found that the PDP-11/83 was about 33% faster than the PDP-11/73. About 20% was due to using the PMI memory (which usually works with the PDP-11/73 boards as well) and about 13% was due to the faster crystal on the M8190-AE board. If you have any more questions, please ask. Jerome Fine