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Date: Tue, 12 Mar 1996 01:48:34 -1000
From: richard@pegasus.com (Richard Foulk)
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In-Reply-To: J Wunsch <j@uriah.heep.sax.de>
       "Re: Slow Toshiba 6.7X cdrom drive." (Mar 12,  9:42am)
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To: joerg_wunsch@uriah.heep.sax.de (Joerg Wunsch),
        rgrimes@gndrsh.aac.dev.com (Rodney W. Grimes)
Subject: Re: Slow Toshiba 6.7X cdrom drive.
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        freebsd-hardware@FreeBSD.org
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} > Try the 3 following dd commands, I found that xfer rates on multispin
} > cdrom drives is heavily block size dependent.
} > 
} > dd if=/dev/rcd0a of=/dev/null bs=512
} > dd if=/dev/rcd0a of=/dev/null bs=2048
} > dd if=/dev/rcd0a of=/dev/null bs=8192
} > 
} > Many drives will due there highest rate with the 8K I/O, a few others
} > seem to like the 2K I/O. 
} 
} The optimum is 8 K blocks (~ 500 KB/s).  When enlarging the blocksize
} again (500 K, dunno how the driver does slice this request), it drops
} to the aforementioned 300 KB/s.
} 

Hmm.  Maybe the driver should be tunable.