[Drives up to 8 GB...] Geez, did DEC ever even make PDP disks that big? In my case, all I'm doing is using RT-11 to make a set of 2.11BSD tapes, and then installing that. Anyway, thanks for the notice. ^_^ -------

Jerome Fine replies: One additional bit of information that is useful is that starting with V5.5 of RT-11, up to 64 partitions could be used at the same time as opposed to only 8 partitions from V5.3 to V5.4G of RT-11. Starting with version V5.5, the MSCP device driver (the LD: as well) allowed extended device drivers and the names D00: => D77: with the two digits being regarded as Octal Characters for a total of 64 (decimal) partitions. You need to either re-boot or UNLOAD and LOAD an MSCP device driver to activate the other partitions if you also have a 9.1 GByte drive like Tim has (slurp slurp slurp). In regard the the maximum size of the drive, the DEC implementation allowed a partition number of 377 Octal (255 decimal) as the maximum since the two word table uses the UNIT for the first word and the second word split (one byte each) between the partition and the port (controller) which is almost a complete waste since the DEC implementation allows only a maximum of four ports in any case (only 2 bits required). Since all 16 high order bits of the 32 bit block number are available, it would be possible (but not trivial) to allow a much larger partition number and make better use of the map table. Since I don't have a 9.1 GByte Micropolis (slurp slurp slurp) for a system with RT-11, I have not bothered to determine how much effort it would be. Tim, maybe you could figure out what code references the PART and PORT values and see if the 2 bits in use for the PORT could be placed at the top of the word and 6 extra bits made available to the PART for a maximum number of 16384 partitions and a 512 GByte drive. While a 512 GByte drive is not yet available, that should be enough for RT-11. I don't know how I would keep track of 16384 partitions?????? If you really wanted to go for broke, why not switch the UNIT and PART values (word for a byte) and allow up to 65536 partitions and a 2 TByte drive. ALSO, be aware that ONLY for first EIGHT map entries in the table can be booted with DEC distributed software and presumably V5.7 from Mentec as well. Changing the map table in the boot portion of the device driver is not only possible, but has been done to allow all 64 partitions on a single controller to be bootable DEC boot ROMs to boot an MSCP device where the physical UNIT number is not the same as the logical unit number in the mapping table. So if the physical drive UNIT number is 3, DU3: MUST be booted if you are using a standard DEC distribution of MSCP or DU(X).SYS device driver. It is also possible to use a different set of letters for the MSCP device driver (but start each different one with a letter different from D and L and the same restrictions apply. The standard DEC boot ROMs will automatically search for alternate MSCP CSR addresses and boot MI0: (if Tim had called his driver MI for Micropolis) and had used ONLY one controller and the drive on the controller or host adapter was UNIT=0 for the hardware. NOTE THAT DEC BOOT ROMs FOR A HARDWARE BOOT CAN NOT BOOT NON-ZERO PARTITIONS. Note that the above is not quite true if 2 active partitions (the first must be PART=0) are available. The secondary boot block can be read from the first drive with UNIT=n for DUn: and the mapping tables used for the actual partition which is to be booted. I don't really consider that a proper procedure, but it could be used in an emergency or even all the time if someone wanted to do things in a non-standard fashion. I just do not feel comfortable with that kind of thing since I want to be able to know exactly what will happen. It is difficult enough to keep track of what is normal. I recommend that dual partition booting not be done. Tim, do you have the search algorithm for alternate CSR addresses when the standard CSR DU MSCP address of 172150 is either not available at all or is a removable floppy with no media present? One of these millennia I want to write an MSCP boot interface that will allow any controller CSR, any UNIT and any PART, but I can get by with what is available right now - I just boot MI0: and then re-boot M45: Sincerely yours, Jerome Fine