8X DVD reader is twice as fast as 52x CDRom

[mraeryceos]

From http://cdrfaq.org/faq05.html#S5-22 :

It has been stated that, at a rotational speed equivalent to about 50x at the inside of a disc, the polycarbonate starts to deform and the disc becomes unreadable. Experiments (e.g. an episode of the "Mythbusters" TV show from 2003) have demonstrated that discs will warp when they get up around 25,000 to 30,000 RPMs. However, recent 52x drives only read data that quickly from the outside of the disc, actually reading at about 21x near the inside. This requires a speed of 10,000 to 12,000 RPM, which is safe for discs in good condition. Reading at 52x from the very inside of the disc would require a speed of about 27,500 RPM, and read data at 137x near the outside.

Incidentally, "1x" on a DVD-ROM drive is 1353KB/sec, which is roughly 9x the speed of a "1x" CD-ROM drive. A 16x DVD-ROM drive reads at a speed equivalent to a 144x CD-ROM drive! The DVD doesn't actually spin 9x as fast, though, because the DVD "bit density" is higher. The drive can read roughly three times more data in a single revolution from a DVD than it can from a CD. (Incidentally, the 1353KB/sec figure comes from the DVD maximum user data rate of 11.08Mbps, where the 'M' is 1000*1000.) For more details, see http://www.dvddemystified.com/dvdfaq.html#4.2.

Well, ok...

An 8x DVDrom 13MB/s is twice as fast as a 36x cdrom speed

Consider that the average for the modern 52x cdroms is 21x in the center (due to max angular velocity) and 48x after somewhere in the middle (max data throughput). After looking at some graphs for the freeware "nero cd/dvd speed", the average bandwidth for 52x cdrom seems to be 36x.

I'm guessing that DVD drives don't suffer the affliction, and can read 8x at any radius on the CD.

If I got all this right, then there is one remaining question:

What speed DVDroms or DVD Burners are out there? What year did the 8x speed become defacto for DVD drives? I read somewhere that DVD drives where quick to increase in speed on the market... so I'm guessing there aren't too many slow DVD drives out there.

Edited October 19, 2007 by mraeryceos

[arctirus]

I just wish the would dump the whole #x speed system. I don't know to know how many X my cd, dvd or flash card is. I want to know transfer speeds in real numbers.

[cyprod]

well, my DVD burner is 18x, though keep in mind that DVDs are thicker and heavier than CDs are, so I wouldn't be suprised if they couldn't be spun as fast. But I also know that DVDs, like CDs, use constant angular velocity at max speed reads so the data rate increases as I get farther out on the disc. I typically see around 5x at the beginning and the outer portions I get more near 12-13x. Of course I haven't rigerously tested this, but this seems typcial for me. And also, I wouldn't consider 8x the standard, most everything supports 16x to my knowlege. And if I remember correctly, they could spin discs faster safely, but the LED is the limiting point from keeping them going any faster.

[phkninja]

cd speed here

dvd speed here

[mraeryceos]

@cyprod: "I typically see around 5x at the beginning and the outer portions I get more near 12-13x."

Are you using Nero CD-DVD Speed to measure that?

Edited October 20, 2007 by mraeryceos