flash (or ide) storage for unibus 11?

As I mentioned, a quick (about 15 minutes) look in the DSD 880/30 manual did not suggest that the RL02 emulation included hardware to support a 22-bit address. My first drive was, indeed, the DSD 880/8, if I remember the number correctly, which did have only the 7.8 MB RL02 reduced drive which you just specified. This reply is confirmation and a bit of clarification that the part number was the DSD 880/8 as opposed to the enhanced model, DSD 880/30, which emulated three full sized RL02 drives. Note that both the DSD 880/8 and the DSD 880/30 included a single RX03 floppy drive. And, of course, both also used a dual module as the controller in the Qbus. Also, as is noted above there must have been a controller for the Unibus. Thank you for confirming that the RL02 emulation supported only an 18-bit address. I saw that model at one point. It was the only one I ever saw, so I did not bother to include 22-bit support in the DYX.SYS device handler - mostly because I would not have been able to test the code. Both the DSD 880/8 and the DSD 880/30 supported double-sided media for the RX03 floppy drive. A check of the DSD 880/30 manual to support double sided operation with V04.00 of RT-11. Inspection of the file, DY.MAC from V04.00 of RT-11, confirms that DEC had code which supported double-sided media and even the CSR specs in the DEC RXV21 controller specifies, as far as I can remember, a bit to determine if the RX03 floppy drive has detected a double-sided floppy in the drive. Note that the DEC RX02 floppy drive did not have that electronics or hardware to detect double-sided media. It is possible that DEC did produce an in-house RX03 drive, but I am not aware of DEC actually selling RX03 drives to customers. PLUS, the code in the file, DY.MAC from V04.00 of RT-11, has bugs (at least in the distribution copy released with V04.00 of RT-11) which would prevent the correct operation of a double-sided media. One other point of interest is that by 1983 when DEC released V05.00 of RT-11, the extra code with support for double-sided media had been removed from DY.MAC. It probably should be mentioned that a different position is used for the index hole for double-sided media (about 1/2" more to the right) as opposed to the location of the index hole for single-sided media. The DSD 880/30 RX03 floppy drive has TWO detection circuits in the two possible positions to determine which media was present in the drive. Because every floppy media that I ever saw has been coated on both sides and could support double-sided operation even if the index hole was in the single-sided location within the cardboard jacket, I experimented with adding the index holes required for double-sided operation and covered up the single-sided index holes. After that worked successfully, I became disappointed that I had to deface the floppy media with the extra holes. The simple solution was to use a DPDT switch and flip the detection circuits so that the RX03 drive would signal a double-sided media what there was a single-sided index hole and the DPDT switch was in the alternate position. To add to the success of that extra switch, the DSD 880/30 supported an off-line LLF (Low Level Format) which, of course, no DEC controller ever supported for 8" floppy media. In answer to the question of support for double-sided media, there are two methods of using both sides of the floppy. One method is to read all of one side, then read all of the other side of the floppy media. The second method is to read both sides of the media for each cylinder, then increment to the next cylinder. Based on the code for DY.MAC which was present in V04.00 of RT-11, DEC choose the former method. It seems possible that if you were using floppy media written via one method and read by the opposite method, there would obviously be some confusion. The SMS-1000 (I hope I have remembered the part number correctly) includes an 8" RX03 type of drive which can handle both single-sided and double-sided media - although the built-in controller is MSCP based and both the internal hard drive and the single RX03 floppy drive are considered DU: or MSCP devices under RT-11. When single-sided floppy media are used, there is no difficulty. However, if an 8" media that is double-sided is inserted and files are written to that floppy, the results can'r be read on the DSD 880/30 using a modified DYX.SYS device driver which supports double-sided operation since it is quite obvious that the MSCP controller in the SMS-1000 wrote both sides of the floppy before changing cylinders. This might have been the cause of the problem between the two floppy drives. I agree it is doubtful, but I can't think of anything else. FINALLY, due to the 18-bit address restriction with all DYX.SYS device drivers under RT-11, I added code to support a bounce buffer that allows the user buffer to be in a 22-bit location, but still be able to support DMA to the silo on the controller. The bounce buffer must be in the first 256 KB of memory, but the device driver performs the extra transfer one word at a time between the bounce buffer and the user buffer if the latter is above the 256 KB boundary. Jerome Fine