CD-ROM on RT-11?

Jerome Fine replies: Since I have used a CD burner for only a month, I was limited to the experience of using only the RT-11 Freeware CD from Tim Shoppa. Also, since I had only an IDE CDROM drive on a PC, my experience using the CD was only under E11 under Windows 95 and Windows 98. I did try and connect a SCSI CDROM drive to a Qbus CQD 220/TM on a real PDP-11, but was not able to get it to work. More recently, I think I have been able to copy a file which had been tested to see if it could be used to successfully boot RT-11 (under E11 under Windows 98). I copied that file to a CD and was able to "View" all of the blocks on the CD in their correct locations on the CD using Nero Burning, but I was still not able to boot RT-11 from the CD. One key aspect to realize is that RT-11 knows only about blocks that are 512 bytes. Since a CD has a 2048 byte sector, that problem must be overcome, but is not the only problem. Fortunately, a CD is a READ ONLY media, so problems associated with writes don't ever arise. One problem that RT-11 does not have is that the drive media is not required to be writable, although there will sometimes be SWAP errors after a program exits - which can be avoided by using the command SET EXIT NOSWAP All I am saying is that a CDROM drive is not a supported drive under RT-11. And while I am sure that it is possible to write a file which is a bootable image to a CD, the correct combination of hardware is not well specified in my mind. If you are actually able to boot RT-11 from a CD, it would be appreciated if you would tell us the specific hardware components which you used along with the software version of RT-11. One aspect to note for V5.03 of RT-11 is that you may be able to read a non-zero partition, however, the standard DEC distributed MSCP device driver is UNABLE to boot from a non-zero partition. So if SET DU1 UNIT=0,PART=1 COPY/BOOT DU1:RT11XM.SYS DU1: are used with V5.03 of RT-11, it is impossible to boot from DU1: using the DEC version of the MSCP device driver. This is not a problem with V5.06 of RT-11, so obviously it is a software bug. Using Exchange under VMS had certain annoying limitations the last time I used it. While it was possible to MOUNT the file or the drive as "/FOREIGN", there was no variable to specify the partition. Thus the default was ONLY partition zero. It was possible to circumvent this problem with a hard drive that is also compatible with PDP-11 hardware (the only one I know of is a SCSI hard drive or a removable media such as Magneto Optical), but it was not simple. One problem you may have with the downloaded DEC distribution of V5.03 of RT-11 is that the boot block zero assumes an RL02 disk drive. If you copy it to an MSCP media, then you must COPY/BOOT DU0:RT11XM.SYS DU0: if you are going to do a hardware boot. However, if you can first boot from the floppy under V5.03 of RT-11 (which also poses a problem - but not too difficult), then you can do a soft boot via the command: BOOT DU0:RT11XM after which you can then set up the boot blocks via COPY/BOOT DU0:RT11XM.SYS DU0: Some information helpful to understand the boot process under RT-11. (a) In a hardware boot, the primary program in the EPROM is used to read BLOCK ZERO on the specified disk drive media. (b) The secondary boot program in BLOCK ZERO is usually read into memory locations starting at address zero and normally the first word MUST be the NOP instruction. (c) In RT-11, the secondary boot program then reads the tertiary boot program in blocks 2,3,4,5 of the disk drive media and those 4 blocks are sufficient to read the specified monitor and device driver files. Sincerely yours, Jerome Fine -- If you attempted to send a reply and the original e-mail address has been discontinued due a high volume of junk e-mail, then the semi-permanent e-mail address can be obtained by replacing the four characters preceding the 'at' with the four digits of the current year.