From: Rob Bell (rbell1_at_csc.com)
Date: Mon Apr 03 2000 - 17:27:11 EDT
Thanks for the reply. I do have a few comments, though.
"sehh of H.I.C. & D.B.S." wrote:
>
> On 29 Mar 00 10:47:17 CST, Rob Bell wrote:
>
> >Have any of you checked the actual speed of your ThinkPad CD-ROM drive (or
> >DVD)? I just ran a check with a tool called CD-ROM Drive Analyzer v2.1.1,
> >available from ZDNet. It reported that the 24x CD drive on my 770 was running
> >at exactly 12x transfer rate (on a standard software installation CD, not a
> >CD-R or audio CD). This surprised me.
>
> Remember that the speeds marked on cdroms are just the MAX speed using a
> specific cd. What i mean is that a CD filled with 600megs will give you a different
> speed rate than a 50meg CD. The speed varies on the 'place' that the laser is reading,
> so higher speeds will be reached if the laser reads closer to the 'edge' of the CD and
> slower to the 'hole'.
Yes, I understand that. However, the program I used tested block-read
speeds across the whole disk (which was almost full, at 560MB). Reading
the inner sections was slower than 12X, but the max speed was reached by
about the middle, and then it stayed constant across the rest of the
disk (at 12X).
> Another thing is the spin-up delay, which many programs may interpret it as a delay
> of the CD to read. Its because very fast cdroms need a bit more time to reach max
> speed. So in the end a 20x speed cdrom may be faster than a 50x when it comes
> to read in bursts and the cdrom has alread spinned-down.
Not an issue with the type of test that this software did.
> You should tolerate cdroms at about half the reported speed. Although most
> of them don't even reach that much. Typical marketing stuff.
Unacceptable. If it's rated at 24X (max) then at some point reading a
full disk it should approach that speed (for a factory stamped data
CD). The X rating specifies a certain amount of data that can be read
per second (150K/s = 1X, I believe). If the unit can't produce at that
speed under some circumstances then it shouldn't be rated as such. I
know this happens in a similar way with hard drives (marketing says 40GB
meaning 40,000,000,000 bytes instead of 42,9xx,xxx,xxx), but if they
really gave you 20GB instead of 40GB you'd send it back.
Rob
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