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Hardware

Establishing the Maximum Speed of a CD-ROM Drive 495

Posted by michael from the science-at-its-finest dept.
UnknownSoldier writes "Ever wondered how fast CD-ROM drives can spin their CDs before the CD will self destruct due to centrifugal force? This person was too, and has his results. (So much for those 100x drives)."
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Establishing the Maximum Speed of a CD-ROM Drive More

Establishing the Maximum Speed of a CD-ROM Drive

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  • Who would want a 100x drive? I think I've sustained permenant hearing loss from the whine of my 32x drive.

    • Re:Who would want one? (Score:4, Informative)

      by hendridm ( 302246 ) on Saturday April 20, 2002 @01:18AM (#3377958) Homepage
      32x might be exxagerating a little, but I know my 50x sounds like a jet engine taking off when it spins up.

      Future drives will have to take advantage of technologies like TrueX [cdrinfo.com] to be tolerable.

      Then again, how fast do I really need my CD-ROM to be? I mean, I only use my CD-ROM to 1) reinstall the system and 2) to play music. A 32x CD-ROM is plenty fast to accomplish both of these tasks.

      The point of this experiment wasn't to push technology but to do something silly to wow your geek friends. (Then again, I didn't read the link since it was Slashdotted after a measely 6 posts).
      • 32x is not exaggerating...I often stick a knife between my drive and the drive plate cover above it to kill some of the vibration. :)

      • Re:Who would want one? (Score:2, Funny)

        by Anonymous Coward
        I only use my CD-ROM to 1) reinstall the system and 2) to play music. A 32x CD-ROM is plenty fast to accomplish both of these tasks.

        I only use my CD-ROM reader to play MP3 CD-R. Where can I get a 0.1x drive?
      • Once upon a time a client of mine bought a then-SOTA Toshiba CDROM (I think it was a 32x). When it first fired up, the noise was so loud it didn't register as coming from the computer -- I kid you not, we all ran to the window to see what the neighbour was blowing up on his backyard hotrod. Needless to say, that one went back to the store.

        Conversely, I have a 50x Acer that is almost silent -- it's not as loud as the case fans (which aren't too bad in that machine).

        I'd made a guess a while back that 50x was probably nearing the practical limit for a CDROM drive of current technology, and seems I wasn't too far off.

    • Re:Who would want one? (Score:5, Interesting)

      by mgv ( 198488 ) <Nospam.01.slash2dotNO@SPAMveltman.org> on Saturday April 20, 2002 @01:25AM (#3377982) Homepage Journal
      Who would want a 100x drive? I think I've sustained permenant hearing loss from the whine of my 32x drive.

      The biggest problem with these sort of drives is seek time. A modern drive can read the whole CD in under 2 minutes, but it will take a good fraction of a second to jump from one part of a drive to another. This doesn't improve alot no matter how fast you spin the CD.

      A far better solution would be to build a CD with a 640 MB Cache, and have it just read the whole thing into RAM.

      Given the price of RAM over the next few years, this sort of technology should available soon.

      Alternatively, it could be written into the OS itself. The only problem with this could be with some copy protection systems perhaps.

      Michael

      • Re:Who would want one? (Score:5, Insightful)

        by Waffle Iron ( 339739 ) on Saturday April 20, 2002 @01:50AM (#3378087)
        The biggest problem with these sort of drives is seek time.

        The slow seek time doesn't bother me nearly as much as the eternity it takes from the time you insert the CD in the drive until the time it is ready to send data. In fact, I'd probably be happy with an 8X drive if it had a < 1 second delay between hitting the close button and viewing the README file.

      • well this is not entirely true... although it is true that a cdrom needs time to position the laser lens over a sector that is not very much of the time... your thinking too much like hard drives... in a hard drive you get fragmentation which means the head must spin all over the place gathering all the data into one file... there is no fragmentation of cdroms as they are used more and more... so a hard drive uses a combination of sequentail AND random IO's where as a cdrom uses mostly seqential IO... and manufacturer's usually measure their cdrom by the spinm spead which is not a true test of speed... a cd can spin real fast but it wont read that fast sometimes and in fact the only thing that helps is positioning the lens... so what you really need is a high quality drive... dont skimp on the drive... get a name brand drive... it really does help... personally i like tishiba cause they make a fairly good cd-rw/dvd drive that is cheap but when looking around try to find out some REAL info about the cdrom not just some post X speed...

      • Re:Who would want one? (Score:2, Insightful)

        by Anonymous Coward
        Apparently, there's a lot of youngsters here that didn't keep-up with the CDROM market about 8-10 years ago. When 4x drives first started appearing, you saw a divergence of the top end specs. One group went towards faster real-life performance and the other went towards faster paper performace. The NEC drives represented the first group. They could read the disk at 0.2X (if I remember correctly) and continue to read it until it hit the maximum of 4X. According to the manual, the seek time is 110 ms. The latency was very low for reading small amounts of data because the head moves quickly and it doesn't have to wait on the drive to speed up to full-speed. In addition, it can read the disk as it is accelerating. This is the drive I've used for seven years and counting. The second group is represented by the cheap Tiawanese clones that kept advertising higher and higher X speeds with much slower seek times than the drives 7+ years ago! The 32X drive I bought at Best Buy last week has almost twice the seek time as my 7 year-old NEC drive. I don't understand how marketing has so completely outplayed engineering when it comes to CDROM performace. The 7 year-old NEC's are much, much faster in real-world use than the new 52X drives. Of course, when installing RedHat a 52X is fast, but you don't do that nearly as often as you read a few bytes.z

      • Re:Who would want one? (Score:3, Interesting)

        by mandolin ( 7248 )
        Alternatively, it could be written into the OS itself.

        This is actually what happens with Linux; it's called the buffer cache and page cache. One's (disk-)block oriented and the other's (memory-)page oriented. They work (well) with other media, too. I'll stay scarce on the details since a) I don't know them and b) it's probably changing in 2.5

        Lots of SCSI disks, controllers, and (yes) cdroms have their own ram cache. Just not 640MB worth.

    • Re:Who would want one? (Score:4, Interesting)

      by rneches ( 160120 ) on Saturday April 20, 2002 @02:03AM (#3378125) Homepage
      A long, long time ago (like, 1992 or thereabouts) I scribbled out a design for a CD-ROM that I calculated could do 100x fairly easily, although that wasn't my intention in the design. I was trying to find a way to prevent portable CD players from skipping, eating batteries, and otherwise sucking.

      Basically, you hold the CD still in a little bracket, and spin a tiny little curved mirror around at the center. Since the laser will bounce erratically off the surface of the CD, you would read from the disk by placing a thin glass or plastic cover over the CD with a few photosensors sensors around its edge. The returning laser (carrying the data) could strike the cover at any pount, and the internal reflection of the cover would get enough of it to the photosensors to read the data. The laser will zip all over the place, so you'd use timing to ignore the data from non-contiguous parts of the disk. The mirror could be as small as the diameter of the laser, so you could spin it much, much faster than the CD iself could withstand.

      The only problem I counld think of for such a device is that I don't think normal optical media will work as expected if you read it at a low angle.

      Clearly, since no one seems to have done it, it's not that great of an idea. There's probably something wrong with it that I didn't think about at the time. Oh well - I was 12, and I just wanted to listen to Paul Simon without having to worry about bumping the desk while I was doing my cursed multiplication tables.

  • cd glue (Score:4, Funny)

    by ddent ( 166525 ) on Saturday April 20, 2002 @01:09AM (#3377920) Homepage
    Will the next computer snake oilish product be 'cd glue' to prevent you cds from falling apart, citing this paper? :)

  • Google cache (Score:5, Informative)

    by awptic ( 211411 ) <infiniteNO@SPAMcomplex.com> on Saturday April 20, 2002 @01:12AM (#3377931)
    The google cache for this page is here [google.ca]

  • If you want to go even faster (Score:5, Funny)

    by Anonymous Coward on Saturday April 20, 2002 @01:13AM (#3377934)
    you could spin *both* the disc and the reading head (in opposite directions).
    • Interesting idea. What would the max spin be on the laser tho? and would stablizing the laser in its spin be difficult or even worth the added read speeds? More importantly, would this cost more than the whole cache-approach? Hell, you could probably afford cheap RAM for the cache for around what a harddrive would cost for the job, resulting in unreasonable drive speeds. Imagine a Red Hat installation in 10 seconds.
    • Wouldn't the centrifugal force of spinning the laser head move the laser head? It does have mass, so it would have to be counterbalanced.

      Also, the counterbalance would have to move in/out at the same rate as the laser head, or it would get unbalanced.

      • It's an interesting idea, though. The nice thing is you can always increase the strength of the spinning structure, where just spinning a CD limits you to the strength of plastic.

      • Re:If you want to go even faster (Score:4, Insightful)

        by GregWebb ( 26123 ) on Saturday April 20, 2002 @05:53AM (#3378518)
        If we have to counterbalance it, wouldn't the simple solution be to make the counterbalance a second read head and quadruple the speed for a given RPM, albeit needing rather more powerful motors.

        Personally I think this is all rather silly given how little RAM cost now. It would seem more sensible to stick 700MB of consumer DRAM in the drive and cache to it if you need the speed that badly. Cacheing time of 2-3 mins maximum and then many thousand times the original speed with lower power requirements, wear and tear on the disc and drive and noise and vibration levels.
    • and put the CD on the true north pole and read it from a...

      never mind. that's retarded.

  • You can make them faster... (Score:3, Insightful)

    by Shiny Metal S. ( 544229 ) on Saturday April 20, 2002 @01:13AM (#3377936) Homepage
    ...with more lasers.

  • What about external support? (Score:5, Insightful)

    by jelle ( 14827 ) on Saturday April 20, 2002 @01:16AM (#3377948) Homepage
    - 6 replies here and the site already is slashdotted.

    Anyway, I think you can make cd drives that spin 4000x if you want, because it might be possible to put the cd in braces to hold it together, and/or to rotate the laser instead. Or how about using multiple lasers?

    It's just like silicon transistors: There's always somebody saying there is a final physical limit we'll reach within the five years...

    Often, we(they)'ll find a way around the limitation.
    • Instead of rotating lasers, how about rotating mirrors?
    • What i'm waiting for..

      are scratch-resistant CD's. or CD's you can pull the outer layer off of to reveal a new shiny surface. I treat my burnt cd's like shite, so its my own fault.. but still.

      what isn't my fault is old cd's who's upper reflective layer begins to flake off.. cheap sons of bitches made in 1997 just arent sufficent. I lost my entire backup of por..err, my 600mb hard disk.

    • Or how about you read the article (Google Cache, perhaps?)... you'll find that they suggest using multiple lasers or a CCD to read 100 tracks at a time.
    • They tried a disc made out of kevlar, still destroyed it. Aye..
    • One way around the limitation is to increase the spatial density of the data stored on the disc, like DVD for example. A DVD spinning at the same rate as a CD can be read almost 4 times as fast, because the data is packed 4 times as tight. Hard disk drives can read incredibly fast at 10k-15k RPM because of their incredible spatial density. Of course, also mentioned in the article was the multiple lasers method, to read and cache multiple tracks simultaneously. The point is, the CD format was designed in the 1970's; we've come a long way since then. It's about time to stop using CD's and go to DVD's or whatever the next gee-golly medium is.

  • Depends on the age of the CD (Score:5, Interesting)

    by Taco Cowboy ( 5327 ) on Saturday April 20, 2002 @01:17AM (#3377956) Journal


    Contrary to popular belief, plastic doesn't last forever.

    And since CD is made up of two layers of clear plastic, sandwitching a thin wafer of metal media inside, the more the CD is aged, the weaker the plastics of the CD become.

    And so, the maximum spinning speed for a CD depends on how old the CD is.

    I do have some pretty old CDs from the early 80's, and I will NOT put them in my 52X CDROM drive. Unless of course, I want to scrap bits and pieces out of my machine. :)

    • I do have some pretty old CDs from the early 80's, and I will NOT put them in my 52X CDROM drive. Unless of course, I want to scrap bits and pieces out of my machine. :)

      You probably already know this, but just for the record -- unless you have a defective CD drive, it shouldn't ever try to spin an audio disc up to full speed unless you're doing digital audio extraction. If you're merely listening to your CD, it will spin at 1X, just like any standard CD audio player.

      • My experience (Score:3, Insightful)

        by Taco Cowboy ( 5327 )


        You said:

        "You probably already know this, but just for the record -- unless you have a defective CD
        drive, it shouldn't ever try to spin an audio disc up to full speed unless you're doing digital
        audio extraction. If you're merely listening to your CD, it will spin at 1X, just like any
        standard CD audio player."

        My experience with my CDROM and CDRW drive (Samsung 52X CDROM drive and Sony 16X/10X/40X CDRW drive) is that whenever I put a disk into it, during the SEARCH, the drives will SPIN VERY FAST - I can even hear the whrrrrrlllll sound ! - then it'll slow down, if the drive finds out that the disk is an Audio CD.

        What matters is that my OLD audio CDs may NOT even survive the FAST spin during the SEARCH routine.
    • Contrary to popular belief, plastic doesn't last forever.

      Thats true CD's might be no permanent storage medium. However lifetime of a well handed CD is still unknown as the CD's out of the 70'ies still work fine. Maybe it are mere hundred years, maybe just 50 or forever. Who knows? My grandchilds will :o)

  • Why even spin the disk at all? (Score:5, Interesting)

    by gnovos ( 447128 ) <gnovos@ c h i p p e d . net> on Saturday April 20, 2002 @01:23AM (#3377978) Homepage Journal
    That is old technology, trying to mimic an LP and it needs to be changed!

    Instead of spinning the disk, just have one laser suspended above the CD with a splitter that alters the direction of the beam, like maybe similar in concept to a cathode ray beam. Have the "read" sensor at the focal point of a parabolic mirror covering the top of the cdrom case and fire the laser at whatever angle it takes to hit position X. The beam will bounce off the pit and either scatter or reflect back up into the mirror striking the focal point, with seek times limited only by the speed of light! Forget 100X, if you did it this way you'd be looking at 100,000,000x speeds from CDs that don't even move an inch!
    • Something like this might be feasible, theoretically, but in practice you'd never ever see something that cool in a consumer device. The number of precision parts and finely-ground mirrors, plus the fact that *exact* manufacturing accuracy would be required or the resulting product wouldn't even function, means that the cost of a device like that would be astronomical.

      Even so, I doubt a parabolic mirror would work. It seems like it would diffuse the laser light too much.

      • Re:Why even spin the disk at all? (Score:5, Funny)

        by wo1verin3 ( 473094 ) on Saturday April 20, 2002 @01:39AM (#3378035) Homepage
        something more exact then a laser reading pits and grooves burned into plastic that are invisible to the human eye? Pft...why would CONSUMERS have access to such technology.
        • something more exact then a laser reading pits and grooves burned into plastic that are invisible to the human eye?

          Maybe you should look closer to the CD, I do see them. There is a difference between a burned CDR and a blank one. You can also tell how much space is left on the CDR by looking at it. However yes I deny to be able to read the data with blank eye :o)
      • The focal point of the mirror would have to be far enough away from the surface of the CD so that the angle of incidence is low enough that the laser doesn't bounce off the surface of the plastic. This would make the size of the no-moving-parts CD-ROM drive pretty big.

        This device would also be MORE vulnerable to physical shock then current designs due to the difficulty of aiming at that range. Current designs put the lens of the laser within a few mm of the surface, but with a big mirror it'd be more like 10-20cm. It isn't important that the accuracy of the aiming be high, but the precision does need to be so that no tracks are skipped.

        This device would be useful for recovery of data from damaged disks, but not for everyday use.

    • Re:Why even spin the disk at all? (Score:4, Insightful)

      by seanadams.com ( 463190 ) on Saturday April 20, 2002 @02:22AM (#3378171) Homepage
      with seek times limited only by the speed of light!

      Figure out how to redirect a beam of light in a couple nanoseconds, and I guarantee you'll win a Nobel prize.
      • Well, I can get close. Get tiny strips of that glass that polarize black when you pass a current through it and place them in front of the laser. Behind each strip place a slightly different shaped lens. Polarize all the panes of glass to be black and flip on the laser. Now if you want the beam to go a certian direction, you depolarise only the strip of glass that covers the lens that will point to the position on the disk you want and, tada, seek times at the speed of electricity, which is close to the speed of light. Yes, this is crude, but it shows that there is at least one way to do it, there are probably more too.

      • Re:Why even spin the disk at all? (Score:4, Informative)

        by MadCow42 ( 243108 ) on Saturday April 20, 2002 @10:57AM (#3379145) Homepage
        It's called an "acoustic optical modulator", my old company uses them all the time in their laser photographic printers.

        We modulate a laser beam on the order of 14 million times a second, actually a lot more than that. Check out www.cymbolic.com [cymbolic.com] (LightJet / PlateJet products).

        MadCow.
      • mod the parent down.
        Lithium Niobate Modulaters go at 20 Ghz ( I have one sitting in front of me in a box).
        http://www.eospace.com/
        Hell they even have a 40 Gb/s, but it isn't that good.
        Anyway if you want to redirect the light beam you can use a lithium niobate polarization controller and have polarization dependent componets at the output that only let certain states of light through (and attenuate the rest) and thus you are redirecting the beam down a different waveguide in the ps range.


        I am sure there are easier ways. But it is saturday morning....

    • Re:Why even spin the disk at all? (Score:5, Insightful)

      by anshil ( 302405 ) on Saturday April 20, 2002 @02:32AM (#3378199) Homepage
      The beam will bounce off the pit and either scatter or reflect back up into the mirror striking the focal point

      Thats how you learn how CD`s work in school, but it isn't true. In past it was the classical approach of not telling the whole truth to keep others from copying it.

      First the beam is not scattered or reflected, it is _always_ reflected. The CD consits of two layers, the back one is solid and 100% reflective. The distance between the two layers has to be exactly lambda / 4 of the lasers wave length. Now the first layer is semitransparent. Meaning 50% of the light gets through 50% gets reflected. In the first layer you have the pits representing the data. If this layer has a pit 100% of the light gets reflected, but if it hasn't only 50% get through, get reflected at the back layer and then has a destructive interference with the light reflect first. (That's why the distance has to be wavelength/4)

      I fear that the interference will not work if the light is not angeled with 90 degree on the disk.

      How about using 700 Million lasers, not spinning at all? You could read a CD at once :o)

      • I guess this could be dealt with if it is true, have a piece of refractive glass that sits between the laser and the CD, when the light hits the glass, it will refract down into the CD going in at an angle of 90 degrees.
  • When the disc fractured, there was a sharp bang and the test chamber was filled with shimmering, glittering shrapnel, and our grins were big. We hurried in and mounted the next disc, to be able to shoot again as fast as possible.

    It's too bad the site is /.'ed, because I wanted to see if this lab had any job openings ...

  • Another idea for making CD's faster... (Score:3, Insightful)

    by NanoGator ( 522640 ) on Saturday April 20, 2002 @01:31AM (#3378001) Homepage Journal
    I realize there are technical hurdles with this idea, but I think they are possible to overcome: use varying luminosity bits.

    Right now what they use is On-Reflective Off-Non Reflective. If the laser was able to detect that some of the bits were at 50% reflectivity, then you'd have 2 bits of data for every bit of reflectivity on the surface.

    If one were to get fancier, they could use multi-colored bits. Using 2 lasers instead of one, then one laser would read a different value than the other depending on how the surface reacted to the light. They may already be doing that today with DVD's, I'm not really sure. It's been a while since I read up on it.

    I guess the real point to what I'm saying is that increasing the density of the data and the spin of the disk aren't the only two options.
    • I would bet that it's cheaper and more practical to shrink the bits. This seems to have worked well for DVD.
      • You are absolutely right. There are practical limits, though. You can only take the bits down so low before you have to contain the disk.

        I think they sped up the CD's waaaay too much, though. Imagine if the disk flew apart inside your computer? It'd take out the CD-ROM. Fortunately, it's isolated. Although if that happened in my GameCube I'd be upset.

        At this point I say: make better use of the bits on the CD.

      • Dont forget, if you shrink the (b/p)its, you also must shrink the pit-reader. In this case, the laser. Red is too big. That's why blue and uv are hot. Now here's the fun part... Find a cheap, small blue laser. Good luck.

        And the Fun Family Slashdot Game... Guess the next type of device crippling!! CSS^2
    • Well they are already 50% reflective. Best go and search the internet a bit how cd's _really_ work. Not how you're teacher told you.

      I desribed it very roughly here [slashdot.org]

      It was on a school guide through the CD factory of sony, the guidance first explained the "popular" explanation how CD's work (with reflecting and scattering) and then said, "You're all technicans, right? Okay than I can explain how they _really_ work" (destructive interference of the laser) :o)

  • Another Mirror (Score:5, Informative)

    by hendridm ( 302246 ) on Saturday April 20, 2002 @01:32AM (#3378006) Homepage

    This one has no broken images [137.28.5.50].
  • And I quote...

    The motor power required, some 300 watts, would impose a rather heavy loading on the computer's power supply, though.

    I don't think I'd be comfortable with something spinning that quickly in my machine. If I tapped it accidentally, would it rip through the plastic and come flying out of my computer? Perhaps maiming bystanders? Hmmm...

    The answer is not to spin the disks faster, but rather to read more of the disk in one shot. But that would increase the cost incrementally with each reading device added.

    Generally, people use CDs as a one-shot deal, install to hard disk once and then never use the CD again. Though people would like to read from their CDs faster they don't want to pay 4-10 times as much for a CD Player with the mechanics to read multiple sectors at once.

    Sweat
    • I could see the danger. Have you ever opened a CDROM drive while the disk is still spinning? (Some CDROM drives don't spin down the disc when they are having trouble reading it) I've actually had CDs fly out of the tray when doing this.
  • Looks like the hard drive of their server is feeling the centifugal force as thousands of Slashdotters bombard the site =)
  • I got to thinking about the problems associated with mechanical drives, and it occured to me that there may be an alternative method that has no moving parts. Ever read about how your monitor works?

    The way I understand it, a burst of energy (Proton?) is fired from a gun and electro-magentically guided to hit a phosphor on the screen, causing it to light up. The electro-magentic fields are timed to cause the energy to scan across the screen so fast your brain can't see the flicker.

    Imagine if somebody invented a card that worked like that. It'd look like a credit card with a grid like surface on it. You side it in to a reader, and it uses a similar technique to set bits on the surface of the card. Then another beam is used to read data back off of it.

    If this is possible, the advantage to it is that there are no moving parts, so it could easily last for years. If it's a read only medium like CD, then it is *not* succeptable to scratches or wear and tear.

    Whatcha think, sirs?
    • I've heard of things like this being researched. If I remember right, it seems like IBM was experimenting with trying to store data in some kind of cube using lasers.
      • "If I remember right, it seems like IBM was experimenting with trying to store data in some kind of cube using lasers."

        You mean holographic memory? I remember that too... Curious what they could do with it today. A hologram holds a TON of data. A 2-d plane holds a number of images, just depends on the angle you're looking at it with.

        If we're talking about the same thing, that's not exactly waht I'm talking about. (Although it is very interesting!) I was just thinking there's a way do that on a flat card with no moving parts.

        I need to develop the idea more, though. Somebody in an earlier post illustrated some problems with it. Heh.
  • Then how do they achieve those 52x drives... isn't it dangerous close to that level? (not to mention making a hell of a lot of noise -- linear velocity is on the order of 600 km/h!) Or do they use other tricks (multiple laser heads perhaps, or just very aggressive read-ahead caching?)

  • Do they really need to be that fast? (Score:4, Interesting)

    by Tablizer ( 95088 ) on Saturday April 20, 2002 @01:47AM (#3378073) Journal
    The spin rate seems like it is turning into a consumer numbers game, like CPU speed is/was doing for a while. People who don't know any better compare the raw CPU frequency rates.

    It seems at the higher CD speed it takes too long spin the thing up to reading speed anyhow. If it did not need to spin so fast, then it may be able to get smaller chunks of information sooner.

    Most don't seem to be able to read until full speed is reached. Why can't they read during the spin-up time also? Too hard to calculate?

    Is there a way to set the speed of CD readers slower if one wants this? I have not seen any setting options, but each vendor may be different.

  • You can Do This Yourself with a commonly available Dremel tool like I did; however, I only found the outer tracks would skew at the rated 30,000. Note that the CD hole almost fits the collett of the drill. A little electrical tape fills the gap. A few wraps and there you go. Wear eye protection and do not put anything valuable in the spinning direction, such as your body.

    Was it really 30,000 rpm? I don't know, but I had the 30,000rpm dremel "overclocked" on an inverter at a much higher voltage and frequency. The speed was indeed higher than off 120VAC 60Hz current. Those cheap 300 watt inverters you can get at Walmart can be tweaked with a potentiometer and capacitor on its oscillator circuit. The circuit board layout is very modular and can be quickly seen for modifications. Maximum voltage is around 180 and frequency is around 400Hz before the slew rate overheats the transistors.

    Perhaps I will try again to the point of destructon tonight.

    • Re:DYI cdrom experiment (Score:4, Funny)

      by ProfMoriarty ( 518631 ) on Saturday April 20, 2002 @02:00AM (#3378116) Journal
      I don't know ... you don't happen to teach shop class and have only 7 fingers do you?
      • No, I'm just an electrician at a wharehouse in Kansas City, but I'm trying to blow up a CD again. So far, these things are taking off like UFO's into the air and bouncing off the walls in my "bomb shelter" in the basement. Got one to crack and shell off the silver laminate though.

        With any luck, I'll have an explosion before the night is over. Its all a matter of how many watts I dare to put into this little electric motor.

  • Most Drives ovev 32x use multiple lasers (Score:3, Informative)

    by Anonymous Coward on Saturday April 20, 2002 @01:52AM (#3378092)
    Most (all?) CD-ROM drives over 32X already use multiple lasers to read multiple tracks at once. They usually say "multi-read" on the boxes if they use this technology. Zen research (http://www.zenresearch.com/) invented this technique, and holds patents relating to it.

  • Bla bla bla (Score:5, Informative)

    by SevenTowers ( 525361 ) on Saturday April 20, 2002 @01:54AM (#3378095) Homepage
    Afreey and Infineon already have a 100x (TrueX) CD-Rom drive (25x DVD)" [cdrinfo.com], it came out in 2001...

    This is the future (but who cares, we'll go solid state before it gets popular).

  • Comment: None of the discs reached more than 180 m/s, but on the other hand that's about 650 km/h, the cruising speed of a jet airliner.

    The cruising speed of jet airliners is 800 km/h to 900 km/h, business jets being a bit faster. Today's fast turboprops reach 500 km/h.

  • Black Hole (Score:3, Funny)

    by daidojiuji ( 183833 ) on Saturday April 20, 2002 @02:05AM (#3378135) Homepage
    What they need to do is put miniature black holes in the center of the spindle to cancel out some of the centrifugal force. Also, you could let the black hole out of the CD-ROM drive when you weren't using it and it would clean your room for you!

  • There's no such thing as centrifugal force. (Score:3, Informative)

    by gdyas ( 240438 ) on Saturday April 20, 2002 @02:14AM (#3378154) Homepage

    Sorry to be a physics geek here, but there's no such thing as "centrifugal" force, unless you're talking about the force caused by a centrifuge dropped from a height.

    There IS "centripetal" force, that refers to the force on an object travelling in a circle, which pushes outward from the axis of said circle on an object while it's travelling about the radius. Say you're spinning a ball on a string around over your head. Your work is translated into acceleration around the axis of the circle as the ball spins around your head, but the force is perpendicular to the path of the ball at any one moment, radiating from the axis. This is proven visually by noting that as you put in more work, spinning the ball faster, the angle from vertical of the string the ball's attached to increases toward 90 degrees. See? Force pushing outward, ball moving in circle. When the string is released though (or the CD breaks up) the ball moves in a straight line matching that along which it was travelling at the moment of release -- momentum then is in action.

    To repeat, no centrifugal force. For all our computer learnin', it's surprising that so few paid attention in physics 101.

    • Sorry to be a physics geek here, but there's no such thing as "centrifugal" force, unless you're talking about the force caused by a centrifuge dropped from a height.

      There IS "centripetal" force, that refers to the force on an object travelling in a circle, which pushes outward from the axis of said circle on an object while it's travelling about the radius.

      centripetal force is a force acting toward the centre. in the stone on a string example, it is the force (tension in the string) pulling the stone toward the holder of the string, making it move in a circle. nothing is "travelling about the radius", and nothing is pushing outward from the axis. strings don't push!

      centrifugal force is something you get in rotating frames of reference. one doesn't normally use such frames in physics because they are unecessarily complicated. but that is just a matter of calculational convenience; centrifugal forces are real enough in a rotating frame (it is called a fictitious force because it depends on the choice of frame, rather than being intrinsic. see this page [richmond.edu]). take a fast curve in a car and that fictitious force feels real enough, even if it isn't the simplest way to describe the situation mathematically.
    • According to Webster's [m-w.com], centripetal (from centr- + Latin petere to go to, seek) means "proceeding or acting in a direction toward a center or axis". By this definition, in the ball-on-a-string example, the string provides the centripetal force.

      Webster's also says that centrifugal (from centr- + Latin fugere to flee) means "proceeding or acting in a direction away from a center or axis"

      This is what I remember from Physics 101. However, I may be wrong, seeing as you are the one claiming to be the "physics geek". In any case, however, your definition is contrary to standard, correct English usage.

    • Re:There's no such thing as centrifugal force. (Score:5, Insightful)

      by floW enoL ( 312121 ) on Saturday April 20, 2002 @03:32AM (#3378308)
      There is no "centripetal force." There is, however, a centripetal acceleration, which points *inward*. (Look up the word) You're committing the classic mistake of confusing a force with an acceleration. For example, in your example, the ball's centripetal acceleration is inward. By Newton's 2nd law, a force must be acting on it. The force in this case happens to be the tension of the rope.

      There IS centrifugal force. It's a fictional force, which is a sort of misnomer. A fictional force is nothing but a force felt by an object in an accelerating frame of reference, like a ball on a string (since velocity is changing direction), or a car getting on a freeway (since velocity is increasing). The fictional force in your example would be the one felt by the ball, radially outward, with magnitude equal to the tension on the rope.

      I think it is you who should have paid attention in physics 101.

    • Uncle.

      Consider me educated about centrifugal force being a fictitious force in changing frames of reference. Glad there are some smarties here to set us right.

  • Don't spin the disk at all! Move the laser beam around, and sense pits and lands by reflectivity. You could have a spinning mirror or porro-prism, or you could have a holographic optical element, or a combination of the two to move the beam around. Since the laser beam is massless, this is a much easier solution.

  • Mirror Here (Score:2, Informative)

    by ttyp0 ( 33384 )
    http://www.qedata.se/e_js_n-cdrom.htm [gtlogistics.com]

  • It's easy to get 100x (Score:3, Interesting)

    by pornaholic ( 242268 ) on Saturday April 20, 2002 @02:23AM (#3378176)
    In fact it's basically possible to get instant loads - it only depends on how creative you get.

    Just like the bandwidth vs latency issue in network connections, all we need to do is add more data paths.

    Can't spin the disc at 100x? Well, spin it at 50X and use 2 lasers (I know the first 50x drives did something like this, they were just REALLY buggy at the time). Can't spin at 200X? Use 4 lasers. Can't fit any more lasers in? Take a picture!

    I'm really amazed that we don't have these already actually - we'll need em sooner or later, unless we change to all solid state electronics...

  • Another idea for faster cd reading ... (Score:3, Insightful)

    by x-empt ( 127761 ) on Saturday April 20, 2002 @02:24AM (#3378181) Homepage
    without having to alter existing cd fabrication technologies you could reach much higher speeds if you rotate the cd near its maximum and then rotate the laser in an opposing direction at or near its maximum. Now you can add the two maximums together and you have a MUCH faster cdrom drive.

    Much louder too, of course. But getting cdreaders quiet is easy... its just that manufacturers prefer to make cheap drives instead of quiet ones.

  • A faster way (2,466x) (Score:5, Interesting)

    by labradore ( 26729 ) on Saturday April 20, 2002 @02:38AM (#3378210)

    This is a good way to get a fast CDROM drive:

    1. Buy a 10,000x10,000 dpi scanner with firewire interfeace
    2. Write cdrom image analysis algorithm.
    3. Scan cdrom image into temp hard drive space and analyse, extracting data

    This is based on these rough figures:

    • A cdrom is approximately ( PI*5^2 - PI*0.75^2 )= 76.75 sq. inches of data surface
    • If a cdrom has about 5.6 billion bits on that surface then the density is roughly 76 million bits per square inch.
    • That works out to about 8,800 bits per linear inch. Assume you will need a little better resolution than that because there is some empty space between the dots on a cd surface. 10,000dpi aught to be good enough.

    Assuming that the scanner is faster than the firewire (400Mbps) and 10% overhead for the data transfer, each cd image will be approx. 7.3 billion bits, taking just over 20 seconds to transfer. This device is a 2,466x speed CDROM "drive". Put that in your Pentium and smoke it! Scanner and algorithm design left as an excercise for the reader.

  • Finally!! (Score:3, Funny)

    by Kasmiur ( 464127 ) on Saturday April 20, 2002 @03:09AM (#3378273)
    A use for all those AOL CD's that I have.

    Cause after a while you have enough coasters.

  • What about kenwood? (Score:3, Interesting)

    by Polo ( 30659 ) on Saturday April 20, 2002 @04:26AM (#3378383) Homepage
    The Kenwood 72x drive is quite fast.

    What it does is to spin the drive slower, but read 7 tracks in parallel. Now if they could get two read heads like this, it would be a 142x drive without having to spin the cd any faster.

    [kenwoodtech.com]
    Here's the info.

  • [ukquake] exploding CD-ROM drives (Score:4, Funny)

    by Yarn ( 75 ) on Saturday April 20, 2002 @04:42AM (#3378403) Homepage
    From the annals of the UKQuake Mailing List

    There was a noise from the next office like toast popping, and Steve the senior consultant yelled in terror. "Has your toast popped?" I shouted? "Someone just tried to shoot me!" he replied. I walked into his office to see the occupants crowded around an open CD-ROM drive with the shattered remains of about half a CD in it. As we watched, the drive attempted to shut itself, made it about half way, and then opened again. It repeated this process about twice a minute, shutting a little more completely each time. Eventually it fully closed itself, though it is still opening and shutting regularly. We didn't find the other half of the CD (at least some of it is presumably still in the drive and is what was preventing it from closing) but we did find the front flap of the CD-ROM drive under Steve's desk, where it had fallen having been blown clear across the room, past his head, and colliding with his notice-board.

    Some points:
    • It was a Samsung 40-speed drive. You might want to avoid them.
    • It was a Hewlett-Packard CD-R that had come free with a USB portable CD burner. You might want to avoid them.
    • It was quite warm, though there was no direct sunlight hitting the drive. You might want to avoid that anyway.
    • Fear.

  • Data Destruction (Score:3, Funny)

    by chuckw ( 15728 ) on Saturday April 20, 2002 @04:44AM (#3378410) Homepage Journal
    Seems to me that this would be an excellent way to ensure that your data is permenantly deleted...

  • no... what cd-roms really need (Score:4, Funny)

    by deathcow ( 455995 ) on Saturday April 20, 2002 @06:56AM (#3378591)
    What cd-roms really need is an eject button which doesnt write home to it's manufacturer (at book rates) for permission to eject a damned disc!

    How frustrating it is to push an eject button and watch a device deliberate for several seconds over SOMETHING before ejecting it's cargo!

    Basically, that button means "Your work here is done", so give me the disc, OK??

  • Depends on the brand of CD (Score:3, Interesting)

    by sher0209 ( 246366 ) <sher0209.tc@umn@edu> on Saturday April 20, 2002 @10:51AM (#3379119)
    A friend of mine worked at CompUSA for a couple of months. He said that people would frequently return certain brands of CDRWs because the discs would shatter in their drives. I forgot which brand exactly, but I think it was some of those cool looking black CDs.

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