Newer systems (alpha,itanium) have drivers for SCSI,IDE and USB, that
accept "RAW"-I/O.
That means that it is possible to read and write via SCSI-commands. You
must use IO$_DIAGNOSE
in your sys$qiow-command:
status = sys$qiow ( 1, gk_channel, IO$_DIAGNOSE,
&disk_iosb, 0, 0,
&gk_desc, sizeof(gk_desc), 0, 0, 0, 0);
The pudriver hasn't this capability. The first class driver that accepts
raw commands is the SCSI-driver
(dkdriver/pkdriver).
I have written a writer program for VMS that produces CD/DVD/BLU-RAY and
the VAX-version works
definitely for CD-R(W) and DVD+-R(W).
Eberhard
Am 01.09.2018 um 22:18 schrieb Timothe Litt:
CD's are normally 1024 byte blocks
2048 Bytes/sector is the ISO std for CD-ROMs (Mode 1). Mode 2 omits ECC
for2336 B/sector - but I don't know of a case where someone was crazy
enough to use it for data.
we might have done at DEC was mess with the block size on a CD
DEC does not modify the physical sector format - it is implemented in
the drive.
VMS packs four 512 B logical sectors into one 2048 B physical sector;
the driver handles buffering and provides the illusion of a 512B sector
size. Most FILES-11 CDs use unmodified ODS-2. But distribution CDs
would do things like omit (or truncate) the bit table to save space.
For that reason, ANA/DISK would fail. There are some CDs that use a
slightly modified HOM block (FILES-11 B Level 0), but it wasn't widely
adopted.
There are other oddities - drives & drivers tell different lies about
the geometry (cyl/track/sector) of a CDROM; multiplying these out
frequently will not match the file system's idea of the volume size.
(As recorded in the SCB for FILES-11, equivalent for other formats.)
The lies vary by OS, version, drive & phase of the moon. The same CD
read under different conditions will report alternative facts. These
will not trip up a DEC OS on DEC HW - but can create obscure issues with
simulation - especially if you try to pass geometry from a physical
drive thru SimH.
Writing a CD is rarely supported by a standard driver - typically, CD
writing software issues direct SCSI commands to the drive (encapsulated
in whatever the real transport is). This may be by direct IO, or via a
class driver. It can be somewhat tricky - note that most drives can not
tolerate buffer underruns when writing.
I wasn’t able to figure out how to make it work in RSTS/E.
To be bootable, a CD needs an appropriate boot block (LBN 0). For VMS,
it's written by 'writeboot' - not initialize. I don't remember the
details for RSTS - look at SAVRES->RESTORE and BACKUP for
possibilities. Or wait for Paul K to fill that in.
Also note that dual format CDROMs are possible - 9660 reserves the first
16 sectors for this; thus it's possible to write a disk that is readable
as both FILES-11 and & 9660 (with file data being in the same sectors;
only the metadata differs.) Such disks were actually created.
On 01-Sep-18 15:28, Clem Cole wrote:
below...
On Sat, Sep 1, 2018 at 2:39 PM Zane Healy <heal...@avanthar.com
<mailto:heal...@avanthar.com>> wrote:
Create a virtual disk in SIMH the size of the CD-R blank. Prep
the disk, then burn it to CD-R. This is how I created my bootable
CD’s for RT-11 and RSX-11M+. I’ve then used those CD’s to do
installs on my PDP-11/73. I wasn’t able to figure out how to make
it work in RSTS/E. I could create the CD-R, but not boot and
install RSTS/E from it.
Just curious ... aren't there funnies because CD's are normally 1024
byte blocks and disks are usually 512? IIRC, there are places that
store numbers of blocks (not bytes), and you have to be careful. I
have >>not<< played in any of that in years.
IIRC one of things we might have done at DEC was mess with the block
size on a CD -- that's a Tim Litt type question. Those bits are so
long ago depreciated/garbage collected in my acitve brain cells. ;-)
ᐧ
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