Jerome Fine replies: About 15 years ago, I attempted to produce a WORM device driver under RT-11 called WO(X).SYS for an optical WORM drive. It split the device between the RT-11 directory at the start and the remainder of the device. I seem to remember that I used the Dialog SQ706A in the normal manner for the WORM device which had a separate off-drive controller for the drive and MFM / ESDI set of cables for the actual drive. It actually worked quite well and I still have the media I had to purchase for the test - since once it was altered it could obviously not be used again. All I am saying is that there did not seem to be anything special about the WORM drive / media except for the WRITE ONCE restriction. Otherwise, the SCSI interface acted in the normal manner and once all of the files had been written to the WORM media, the RT-11 file directory was also placed there. At that point, the media was set to be READ ONLY to be protected against accidental WRITEs and used in the normal manner as a standard SCSI drive with the standard DEC DU(X).SYS device driver. Just my experience with hardware that never seemed to catch on very well since READ / WRITE optical drives such as the Sony SMO S-501 appeared within a year or two and made the WORM technology obsolete. As for the original subject which started this thread, I use a CD-R all the time for backup, although it is actually a DVD-R since the backup image file is about 800 MBytes and just a bit too large for a CD-R. Every 4 months, I save the last backup image file of the month to the DVD-R which creates a permanent record with only 3 * DVD-R per year. In addition, if the DVD-R drives / media were not available, I would definitely have used a CD-R for a permanent backup. I have a number of 600 MByte ESDI hard disk drives on the PDP-11 backed up on Sony SMO S-501 drives / media and then transferred to DVD-R media. Since I have about 5 of these 600 MByte files and all fit nicely on just 1 DVD-R with room for a few other files, it was much easier to have the single DVD-R for everything. In general, I regard a DVD-R as just a higher capacity CD-R. Finally, because a CD was actually required and since there is only about 131 MBytes of files, I did produce a CD of RT-11 distributions which is actually able to boot RT-11 directly from the CD-R if the hardware supports 512 byte blocks. As Zane has mentioned, that is possible with some CDROM drives / SCSI host adapters for the PDP-11. In addition, the PC that I use with a Pioneer A05 DVD drive also supports 512 byte blocks with full access to the first 16 CD sectors or 64 equivalent hard disk block which is where the RT-11 directory resides for the first RT-11 partition on the CD of 32 MBytes. I have booted RT-11 as a test on the CD a number of times under E11 although it is just as simple to MOUNT the ISO file for the CD that is on the hard drives - and much faster. Note that before I had the Pioneer A05 DVD, when I attempted to use an IDE CDROM drive, I could not boot RT-11 since the driver prevented E11 from reading the first 64 blocks with the RT-11 directory. Fortunately, I was still able to complete my test of the CD by using a SCSI CDROM drive on the PC and asked E11 to MOUNT the SCSI drive instead. So a CD-R is an excellent media for permanent storage. Just how long it will last is another question. I plan to read my CD-R and DVD-R media every year and test them. In that regard, does anyone else have a regular testing period for their files permanently saved on CD-R or DVD-R and how many years seems to be reasonable? 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.