[Simh] Looking for clues: MAKECD; CDROM format?

[Clem Cole]

On Mon, May 11, 2015 at 8:03 AM, Timothe Litt <litt at ieee.org> wrote:

> That all sounds about right.  Except that the standard sector size for
> CDROM is 2048 (usable, after EDC).
> There's also mode 2, which is 2336 usable, with no EDC. DEC wouldn't have
> used that.
>

​I believe you - as I said these bits have not been loaded into my brain's
frontal lobe cache in many, many years.  I remember High Sierra (which was
standard's group that created the ISO format)​ was mostly dominated by PC
types, hence  8+3, upper case and no file attributes (i.e. MS-DOS format)
ruled.  But I also, I remember it was not 512 bytes per sector, and I
thought it was 1024, but you are likely right.   I do remember, that big
companies like DEC didn't care because they always rolled their own
formats.

The trick was writing them and I can picture the machine we had to do in
the Ultrix lab in ZK03 and I remember it was a real hassle getting it
right.  It was a PC that ran some embedded OS, and interfaces to UNIX via
SCSI.   There was a mode that made it look like a SCSI disk and we would
"access" the "disk" and use the UNIX tape tools to write it via the UNIX
raw device interface.   We then disconnected from Ultrix and then ran some
programs on the system to walk the disk, set it up and then finally burn.
Then take the result to an Ultrix or VMS box to see if it would boot/read
etc before we sent it out for making copies.

I remember that there were a number special things you had to be careful to
do/ways to screw up i.e. making more than a few "coasters" in the process.

As I said, I should see Brian Rich tonight, and he might still have some of
that doc.

Clem
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