> I have a question: I have an UDMA ATAPI CD-ROM, and a VIA MVP3. The bios
> does find and report the CD-ROM as an UDMA drive, and everything is fine
> there. Linux doesn't say a word about it, but I guess that's because
> it only can do that for the haddrives. The CD-ROM is a 36x speed,
> and does only 2.6 MB/sec under Linux ... so I doubt it's running UDMA,
> unless the manufacturer lies about the true speed of the CD-ROM.
2.6MB/s is about half of a full 36x CD-ROM... most really fast CD-ROMs
actually have a maximum angular speed, which results in differing linear
speeds at different radii.
Near the center of the disc the linear speed will be about half of the
speed at the outside. So if the maximum speed is 36x at the outside you'll
see half that at the inside... so you're probably measuring the transfer
rate at the beginning of the disk, at the center.
> Now, how to check if the CD-ROM is running in UDMA mode?
Dunno...
-- brion vibber (brion@pobox.com)
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