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Re: Controlling cd/dvd drive's cache

Well, as I said, my knowledge of CD devices is becoming stale. I have always accessed drives on the very low level, i.e. sending SCSI or ATAPI commands to the drive. Maybe you should do the same Also, the cache size of 2048 sounds weird. A block of Red Book Audio has 2356 bytes, so it could not fit in there.

On the level you are working on, I don't think I have any idea how to help.

Sorry

Alex

Am 13.01.2006 um 16:19 schrieb email@hidden:

Alex (et al),

Thanks for the reply. What I am working on is adding "EAC-like"
functionality (secure cd ripping) to my application
(http://sbooth.org/Max/). In order to perform true error correction and
verify that the audio data is correct, I need to compare multiple reads of
the same sector. Obviously if erroneous data is in the cache then
multiple reads of the same sector will always produce the same result.
Hence the need to either 1) disable the cache or 2) read a block larger
than the cache (2048 on my drive, too large for practical purposes) or 3)
read a sector, flush the cache, re-read the sector, etc. So I am not
writing a device driver per se, just performing some low-level
manipulation.

Stephen

I am not sure on which level you are looking.

My time in CD-Recording is over for  four years now - which is an
eternity in IT. That said, I am sure the MMC3 command set has
commands to do all these things.

However, why would you need to do this? If you are writing to the
device yourself, then you probably came across MMC command sets.

Forcing the cache to be flushed when other applications are writing
to the device is usually not a good idea.

Alex

Am 13.01.2006 um 16:05 schrieb email@hidden:

Hello all,

I had inquired about this a while back and never got a response, so
thought I'd ask again.

Is there a way to control the hardware cache on cdrom drives in OS
X?  For
example, I would like to turn caching on/off, force a flush of the
cache,
etc. It seems there should be an ioctl() to do this.  But, all my
searching has turned up nothing.  What have I missed?
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References: 
 >Controlling cd/dvd drive's cache (From: email@hidden)
 >Re: Controlling cd/dvd drive's cache (From: Alexander von Below <email@hidden>)
 >Re: Controlling cd/dvd drive's cache (From: email@hidden)



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