Microsoft Hybrid Disc Proposal -- Updates

Henry Gabryjelski Henry.Gabryjelski at
Thu Oct 6 14:00:16 PDT 2005

* From the T10 Reflector (t10 at, posted by:
* "Henry Gabryjelski" <Henry.Gabryjelski at>

Dear all,

Microsoft would like to officially withdraw its remaining multi-session
hybrid disc proposal.  As you know, this proposal was created to avoid
data corruption issues when a hardware reset occurs.  We have analyzed
the situations in which this would occur, and believe that proper
firmware design (specifically events during initialization) will prevent
this from being an issue for read-only media for the vast majority of

In addition, my previous e-mail regarding normal READ operation
restrictions on CDROM media was incorrect.  This information was based
on my looking at new Microsoft Windows Vista sources.  So, while reads
past the end of capacity are acceptable for Win2k/XP/Server2003, Windows
Vista will have different restrictions based on the current media type
inserted.  In all cases (including Windows Vista), the READ_CD command
(IOCTL_CDROM_RAW_READ) is never checked for valid LBAs, and must be
properly handled by the drive firmware.  So, there will always be a
method to read from past the capacity of the media.

Thank you for allowing us the extra time to verify that the
layer-switching proposal from Panasonic/Toshiba will not cause the data
corruption issue in a majority of cases.


Henry Gabryjelski

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