From:	"Peter S'heeren" <petersh AT pimc DOT be>
Newsgroups:	comp.os.msdos.djgpp
Subject:	Re: ATAPI command for CD speed change
Date:	Wed, 28 Apr 1999 09:51:06 +0200
Organization:	EUnet Belgium, Leuven, Belgium
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To:	djgpp AT delorie DOT com
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There's a ATAPI command called "Set CD Speed" and it has opcode 0BBh.
You can set the read & write speeds in kB/sec. This is the format of the
command:

+00 : BYTE  0BBh
+01 : BYTE  reserved
+02 : WORD  Read speed in kB/ec
+04 : WORD  Write speed in kB/sec
+05 : BYTE  reserved
+06 : BYTE  reserved
+07 : BYTE  reserved
+08 : BYTE  reserved
+09 : BYTE  reserved
+10 : BYTE  reserved
+11 : BYTE  reserved

All fields are big endian.

I think some drives allow you to change the speed settings the means of
the "Mode Select" command (see: Capabilities and Mechanical Status Page,
code 2Ah). You've to "Mode Sense" first, however, to check out if the
speed fields can be modified.

Good luck

Peter S'heeren



Wolfgang Hesseler wrote:

> I've heard about an ATAPI command for CD drives that can set the speed
> for raw grabbing (audio and VideoCD). I need to slow down the speed as
> I'm getting read problems for contiunuous VideoCD playback. The CD reads
> too fast and spins down the motor which leads to pauses as it always
> takes a few seconds until the drive is ready again.
> I'm doing all this under DOS with MSCDEX. Does anyone know more about
> it or where I can get docs about it?

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