Question about DEC PMI Processors & Gear Acquisition

In the past, I have placed an M8190-AB into the backplane for a VT103 which is a non-PMI serpentine 4 * 4 (four double dual slots serpentine) Qbus backplane. I have also placed that M8190-AB into a BA23 in the third slot position with 2 * 2MB PMI boards in slots 1 and 2. The 3 board configuration is reported by RT-11 as a PDP-11/83 with PMI memory. The system is also about 20% faster than if the 2 PMI boards are placed in slots 2 and 3 and the M8190-AB is placed in slot 1. This would indicate to me that there is a very high probability that all M8190 boards are essentially the same and able to be placed in either an ABCD slot (as with the first 3 slots of the BA23) or an ABAB slot (as with all the slots in the VT103). I suspect that the M8190-AE is named mainly for the 18 MHz crystal which also requires a more recent rev of both the CPU and the floating point chip firmware to be able to execute at the higher 18 MHz speed than the 15 MHz speed of the M8190-AC. So the quick answer is probably that all M8190 boards are PMI capable, but the PMI is not activated if PMI memory is not present in the correct slot(s). In addition, probably all M8190 boards are happy being placed into a VT103 backplane which will not support PMI activation. Of course, I can't guarantee there won't be magic smoke released if the M8190-AE is placed into a VT103 backplane. So can anyone reading this confirm the above? Why are you reverting to a dual board without the boot ROMs? I have tested a VT103 (22 bit upgraded) with an M8190-AB board and one 4 MB quad memory board (obviously non-PMI memory) in the second slot.. It worked very well and no magic smoke was released. The other two ABAB slots had a Quad ESDI controller and a DHV11. It was a great demo system. Obviously the three 600 MB ESDI drives had to be placed outside the VT103 on a separate power supply and I added a fan for each drive as well. Running RT-11 with 600 MB hard drives is enjoyable since there is ample space for files. If the VM: device driver is used as the system disk, it is even possible to power down the ESDI drives, replace one or more of the ESDI drives, then power the ESDI drives back up. You can then UNLOAD and then LOAD the MSCP device driver and just continue without losing anything, although I would ALWAYS close all files on all of the EDSI hard drives first, just as you would if you were using any other replaceable media such as an RX50 or an RX02 floppy diskette. Which Qbus backplane with only ABAB serpentine slots do you have? I do have an M8192-YB which would require adding the Floating point chip. Assuming that you can use the M8190-AE, you can skip the BDV11. The 4 MB of memory should not be too difficult to find. More memory is always helpful. How many slots does you backplane have? Can you find a BA23 box instead and use the PMI memory? With 8 quad slots, you will have no problems with all of those boards. You probably will not forget what you imply you did that makes a replacement necessary. I remember the ":forgetful" moment that I had many years ago with two RD52 drives in a BA23 box when both has the DS3 set. I lost the contents of both drives. Please let us know what the answer is if you hear privately! Jerome Fine P.S. With regard to the response that Glen Slick provided: I notice that while the full capabilities of the module require that installation be made into an ABCD backplane below the PMI memory, there is no requirement that this be done as far as normal operation of the memory is concerned. I seem to remember that Megan Gentry also posted a comment in this regard many years ago and noted that if the PMI memory is installed below the CPU, it will act as normal memory. It is very likely that the comment was made in respect of a BA23 box which has the ABCD backplane for the first three slots, but I could be wrong. In any case, the above portion of the document only stipulates that an ABCD slot must be used to obtain PMI operation (and the increased speed) of the memory. It does not say that an ABAB slot must not be used because damage will occur to the M8190-AE board. Hopefully, someone else will see your original question and state one way or the other concerning the possibility of damage to an M8190-AE when it is installed in an ABAB slot. My guess at the moment is that an ABAB slot will not cause any damage to an M8190-AE, just that PMI memory will function as non-PMI memory without the increased speed. But I could be VERY wrong.