Device Type 5 (DVD-RAM)

Devon Worrell worrell at dt.wdc.com
Tue Aug 19 11:51:45 PDT 1997


* From the T10 (formerly SCSI) Reflector (t10 at symbios.com), posted by:
* Devon Worrell <worrell at dt.wdc.com>
*
Hi,


I think that there are MANY other issues with DVD, not just RAM media.

For example the driver will not be able to access the media because

the READ TOC does not work. So the use of Type 5 is a problem when a
CD

driver is being used.


With a driver that is compatible with Morphing, this will not be an

issue.


I don't know what the schedule for introduction of a Morphing driver

is for systems. Keep in mind that Windows-95/97, Windows-NT, OS2

Unix, MacOS and others are affected.


I would like to hear from the OS folk on this issue, but from my

perspective it should not be an issue. Installing the new driver

|from a DVD drive, can be done from CD media until the OSes are

shipping with a Morphing Compatible Driver.


Thanks,



>>>>

<excerpt>   Currently, the device type for a DVD-RAM drive is set to 5
and was determined some time ago.  An issue exists with regard to
supporting Windows 95 using a DVD-RAM drive.  With devices which are
read-only (CD-ROM and DVD-ROM) there is no problem.  However, with a
DVD-RAM drive, Windows 95 will preempt all the write attempts to the
drive.


   With a device type of 5, Windows 95 issues the following command
sequence:

1.  Test Unit Ready

2.  Request Sense

3.  A couple of test unit ready

4.  Play Audio

5.  A couple of Mode Sense

6.  Several Read TOC


At this point, Windows 95 and Windows 98 prevents writing through the
IOS layer.


I sent a detailed note to Ron Radko at Microsoft, but have not heard
back.  I am hoping that there may be a work around in this area.  We do
not want to bypass the IOS supervisor layer.  This would most likely
have negative affects on other applications.


Has this issue been discussed previously?  If Microsoft addresses this
in Windows 98, what is the concern for backward compatibility to
Windows 95?


Best Regards,

    Rich Vasse

    Software Architects, Inc.

    (425) 487 0122

</excerpt><<<<<<<<


Devon,


    _/_/_/_/    _/_/_/_/    _/      _/ | Devon B. Worrell
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