I am not sure that I understand your suggestion. While I agree that the RX02 was able to switch a single-density floppy to a double-density floppy (and visa versa), the difficulty, as you pointed out, was performing the initial LLF (Low Level Formatting) in the first place on Un-Formatted 8" floppies. That may have been easy with IBM hardware, but DEC made that impossible if all the user had was a DEC system. For readers unfamiliar with DEC vocabulary, the FORMAT command did NOT create a file structure! That command in RT-11 was INITIALIZE and something similar was probably used for RSTS/E and RSX-11. Note that under RT-11, the FORMAT command for the RX02 did NOT perform an LLF, but did set the density bit in each sector if an LLF had already been performed and was sufficiently intact to support clearing out all the data in the sector setting and the density bit to the value requested by the user. In practice, I found that when an RX02 floppy started having problems, the LLF was VERY rarely a problem. For reasons which were not understood, when the floppy media started to have read and or write errors, it was usually possible to have the RX02 floppy drive perform the software command which DEC called FORMAT and re-initialize all the sectors so that the media could be used again without any read and or write errors. That obviously would have required the LLF to be sufficiently present for the software and hardware to repair the problems and reset all the sectors as either single-density or double-density depending on what the user requested. I am not sure what conclusions can be drawn from this example. If it was possible to perform a LLF using the same RX50 drive on the Rainbow, what was the reason why an LLF could not also be performed on a PDP-11? There seems to be a number of possibilities: (a) There was some hardware that the Rainbow had which was missing on the PDP-11 systems (b) The firmware in the controller on the Rainbow supported an LLF, but the firmware in the controller on the RQDX1, RQDX2 or RQDX3 on the PDP-11 did not support an LLF (c) The Rainbow used a program which DEC supplied that could perform an LLF, but DEC did not supply such a program for the PDP-11 systems (d) Another possibility of which I am not aware. Is there an answer as to which possibility supported the Rainbow being able to perform an LLF using an RX50 drive, but that the PDP-11 systems with that same RX50 could not perform an LLF? I don't know how to respond since different individuals will interpret your story in the opposite manner, So I will add my own experience when I used the RX02 drive from DEC along with the DSD RX03 floppy drive. Around 1990 after I had acquired the DSD RX03 floppy drive in a DSD 880/30 system, I also managed to acquire many brands of 8" floppy media. At that point, I had not yet managed to acquire any tape hardware such as the TK25 which supported a 32 MB disk image, so the floppies were my primary backup. I probably had about a dozen different brands of 8" floppies that required an LLF before they could be used. And since a double-density, double-sided 8" floppy media held about 1 MB (1976 blocks) as opposed to about 1/2 MB (988 blocks) for double-density, single-sided media, I set set about the task of enhancing the DEC DY.MAC RX02 device driver after I found the code in V04.00 of RT-11 which included support for double-sided media. What may be called "interesting" was that DEC had removed all of that optional code in DY.MAC by the time V05.00 of RT-11 was released. That might have had something to do with the fact that DEC never sold (that I heard of) an RX03 drive. In any case, adding and correcting the extra code was quite easy. The challenge was to also add support for a user buffer being above the 1/4 MB boundary in a PDP-11 with all 4 MB of memory when a Mapped RT-11 Monitor was used since the controller supported only 18-bit addresses. Another problem was that the index hole for single-sided floppies was offset about 1/2" from the index hole for double-sided floppies. That challenge was solved by using a DPDT switch to flip the sensors that were used on the DSD 880/30 and that supported using, as double-sided, floppies with the single- sided index hole. While a number of 8" floppies had been purchased that had the double-sided index hole, that was less than 10% of the total and after punching the extra pair of holes in single-sided floppies just a few times, it was very quickly apparent that the DPDT switch was a much better one-time solution. What was initially a surprise was that EITHER the single-sided OR double-sided index hole could be used with the same floppy to access the sectors even though the holes were in different positions. The timing did not seem to matter. Only the device driver software cared if the bit was set one way or the other, so flipping the sensors which were activated was an excellent one-time solution when the user (me!!) wanted to use a floppy with a single-sided index hole as a double-sided floppy. In any case, the code was enhanced, my version of DYX.SYS supported the RX03 double-density, double-sided floppy drive under a 22-bit RT-11 monitor. So I set about the job of the LLFs for double-sided 8" floppy media. As mentioned above, in addition to a couple of dozen 8" DEC floppies, I had about a dozen other brands. To make a long story short at this point, the results were "interesting". Every non-DEC branded 8" floppy could hold an LLF for double-sided, double-density. On the other hand, I seem to remember that only about 2/3 of the DEC 8" floppies managed to complete the LLF. The other 1/3 of the DEC 8" floppies could hold an LLF on the normal first side, but not on the second side. Obviously this story was somewhat different since it was not necessary to ask DEC maintenance to make the LLF capability with the DSD 880/30 to work - it already worked. In addition, there was no DEC maintenance contract in the first place and there was no 50 gallon oil drum. There was also no refusal by DEC to enhance the DY.MAC device driver to support the RX03 floppy drive since DEC was not asked. Over the decades since, I have always wondered how it was even possible for ONLY the DEC 8" floppies to be unable to take an LLF double-sided when every other brand managed to do so. There was probably one floppy that was so severely damaged that it would not take an LLF on either side, but that was a specific exception. Any 8" floppy which could take a double-sided, double-density LLF held the data successfully when used in practice. In any case, I also ask the questions: (a) Was it more difficult and expensive to provide pre-formatted disks? (b) FOR WHOM was it more difficult and expensive to provide pre-formatted disks (DEC or the user)? (c) Was it more about customer service and making sure the equipment kept running? (d) Was it more about DEC charging about TEN times the price for pre-formatted disks over the price for un-formatted disks and having a technician take the time to do the LLF (about 2 minutes for each double-sided, double-density floppy or about 30 floppies an hour)? At the time, I seem to remember that a box of 10 pre-formatted 8" floppies from DEC was about $ 50 while a box of 10 un-formatted 8" floppies was about $ 5 a box. If a technician could format 3 boxes of 8" floppies in an hour, that would seem to save that user about $ 135 which would probably be less expensive for the user. (e) Was it equally reliable and less expensive to use non-DEC unformatted 8" floppies if the user had the necessary hardware and or software to pre-format the floppies? Also, I want to be sure to add that in my experience, RT-11 is probably the best written and documented operating system that I have encountered. While there are still a few bugs that can actually crash the operating system and many enhancements were and are still needed, RT-11 is mostly stable and easy to use. RT-11 obviously lacks any security when running under an UnMapped Monitor since the user has access to all of the memory. Even with a Mapped Monitor, a user program can gain access to the Monitor. But RT-11 was not designed to be secure in the first place. So I still think that DEC did an exceptional job - especially since almost all programs written for the very first version of RT-11 can still run under the latest version. Jerome Fine