CD-ROM on RT-11?

From: Tom Leffingwell <>
Date: Thu Apr 4 14:04:22 2002

        I think what I'll do at this point is try to make an image with
exchange of v5.03 with my program and all, and copy as well as copy/boot
it to a scsi disk on the vax, and then move it to the PDP. Assuming I get
far enough to get that working, I'd then experiment with getting it on the
CD. I did end up coming across a Viking/QDT SCSI controller, but it
doesn't have bootstrap, and I don't have a BDV11, nor do I have room for
one. I may buy a CQD-200, as they are a lot cheaper than the the CQD-220.
I'd be willing to trade the Viking if anyone wants to swap.


On Thu, 4 Apr 2002, Jerome H. Fine wrote:

> 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
> 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
> 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.
> > I did finally manage to get my RX02's copied to a VMS machine. The guy
> > that was helping me (who had the vax/vms machine) was out of town for
> > awhile. Anyway, we copied an image of a bootable floppy to the VMS
> > machine, and back to a new floppy, which booted fine with no need to
> > copy/boot it (since the imagine was already that way). We also used VMS
> > exchange to may .dsk files. I need to read up a little more on exchange,
> > but I was thinking if I can work with the .dsk imagines of the ftpable
> > RT-11 5.03, I should be copy in my program and then copy that to a SCSI
> > disk, make sure its bootable, and then make an image of it. The .dsk
> > files seem to be little file on file systems as opposed to just making an
> > image.
> 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
> 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:
> after which you can then set up the boot blocks via
> 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
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Received on Thu Apr 04 2002 - 14:04:22 BST

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