OPC parameters

Dimiter Popoff tgi_earth at yahoo.com
Tue Jan 31 15:55:00 PST 2006


* From the T10 Reflector (t10 at t10.org), posted by:
* Dimiter Popoff <tgi_earth at yahoo.com>
*
After I posted my question yesterday, and, well,
after some more reading of MMC-5, I must say the
document is stating clearly enough that the
right thing to do is to use the GET PERFORMANCE
command (in fact, it is about the only thing one can
do :-) in order to obtain the usable write speeds.

 SEND OPC PARAMETERS is unlikely to be obsoleted
because it is the only way to set a desired write
speed (at least the only way I could find).
 The DoOPC bit will probably also stay useful in the
future as it provides means to initiate device
calibration regardless of its former related state.
On the other hand, there is no problem to send
the OPC parameters with all zeros following the
speed word (and DoOPC set to 0), the target
then (at least the one I have here...)
just does the calibration if necessary
when it receives the next write command prior to
beginning of the actual writing (calibration
takes several seconds, I would say about 5, so there
are no timeout issues with that that I would 
be concerned about).

Dimiter

------------------------------------------------------
Dimiter Popoff               Transgalactic Instruments

http://www.tgi-sci.com
------------------------------------------------------



--- David Burg <daviburg at windows.microsoft.com> wrote:

> This is more a question than an answer:
> 
> Isn't OPC set by the host going obsolete and
> replaced by automated and
> transparent OPC within the device alone?
> 
> Best regards,
>  
> David Burg.
> 
> -----Original Message-----
> From: owner-t10 at t10.org [mailto:owner-t10 at t10.org]
> On Behalf Of Dimiter
> Popoff
> Sent: Monday, January 30, 2006 7:22 PM
> To: t10 at t10.org
> Subject: OPC parameters
> 
> * From the T10 Reflector (t10 at t10.org), posted by:
> * Dimiter Popoff <tgi_earth at yahoo.com>
> *
> I am trying to figure out how to discover which
> write
> speeds are to be used on a given disk.
> I read MMC5 and it does a great job (I am almost
> finished now), here goes my question.
>  With a new disk just inserted there are no OPC
> entries 
> in the data returned by the READ DISC INFORMATION
> command.
> After I issue a SEND OPC INFORMATION with no data (0
> transfer
> length) and the DoOpc bit set to 1, the drive does
> some work
> and next READ DISC INFORMATION returns some OPC data
> which look good (sligthly different for different
> disks etc.).
> However, there is only a single OPC descriptor
> there;
> whereas using the GET PERFORMANCE command with a 3
> (i.e. OPC info requested), I get are a number write
> speeds,
> different on different disks (media).
>  How do I find out which speeds to send with an SEND
> OPC
> INFORMATION command in order to selece and calibrate
> for
> one of the speeds the disk is meant to? GET
> PERFORMANCE 
> will do the job, but it is mandatory only for
> streaming
>  devices, presumably it might not be there on some
> (not a
> big issue for me, I have - alas - no large volumes,
> but 
> I am trying to do the right thing if the extra cost
> will
> not be too high).
> Just sending all thinkable speeds with DoOpc? I have
> not
> tried that out still but it will likely waste too
> much
> time - I am not sure the drive will know which
> speeds
> make sense to work on at all and which not, what if
> it
> decides to blindly do all - most of them probably 
> inapplicable - speed calibrations.
> 
>  Thanks in advance. I realise the answer is probably
> in the MMC5, but well, it has become pretty bulky
> over the years and I would welcome some help, I
> believe
> I ask the obvious to at least some of you.
>  And I guess here is the right place to thank the
> group
> for making the documents good as they are.
> 
> Dimiter
> 
>
------------------------------------------------------
> Dimiter Popoff               Transgalactic
> Instruments
> 
> http://www.tgi-sci.com
>
------------------------------------------------------
> 
> 
> 
> 
> 
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