What is the specification 'X' used for a CD drive?


 I have heard the specification like 52 x for a CD drive. What does the 'X' stand for. Is it speed?  How do we know which specification is best suited for our system. Is it dependent on processor speed. Pls help.
shaan432Asked:
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DVation191Connect With a Mentor Commented:
CD and DVD speeds are measured in "X" units, but the X has a different meaning for each type of drive.

CD X units are equal to 150 kilobytes/second; 1X is fast enough to write a full 74-minute audio CD in 74 minutes.

DVD X units are equivalent to 1.3 megabytes/second, or enough to write a single DVD in about 60 minutes.

Read, write and rewrite speeds are usually different. It is also important to note that the rated speed is usually the 'TOP' rated speed, which is usually not a constant variable, but a varying one.
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sunray_2003Commented:
Hi shaan432,

x = 150 kilo bytes /sec

but it is different for DVD  when you say a DVD has got 8 X speed

SR..
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sunray_2003Commented:
shaan432,
> How do we know which specification is best suited for our system

X is a constant and depending on your application or what you need , you get a CD drive with certain Xs

if your processor is a fast one , you can do job sooner
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grbladesConnect With a Mentor Commented:
Hi shaan432,
52x means the drive is reading 52 times faster than the original single speed cdrom drives. This is 7.8Mbytes/second (52 * 150Kbytes/sec).
Note though that this is the drives maximum speed. When reading the start of the CD (inside) it will be a lot slower.
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joey_the_assCommented:
What's best for your system is the fastest drive you can find.  That will probably be a 48x or 52x, i don't know if slower drives are even manufactured anymore.  And you will get those for dirt cheap, around     $20-$40
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yavoozaCommented:
The cheapest and the best cd roms in the market are 52X ones. You will be better off with a samsung or LG cd drive.

get going
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pjcrooks2000Commented:
X = speed
x is algebraic term that could mean anything really, 1x is half of 2x and 52x is 52 time 1x :)  

good luck sport

pjcrooks2000
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ArlConnect With a Mentor Commented:
Hi,

Just in case, some manufacturers used a trick for having a kind of quicker drive...
The X is like said previously is the number of time that will read the one time speed drive.
And major of the time it's equivalent to 150KB/s, but some manufacturers are decreasing the transfer rate to increase the number of time of reading.

i.e. : a 60X speed drive but with a transfer rate of 100KB/s -> transfer of 6MB/s
But you take a 52x with a rate of 150KB/s -> transfer of 7.8MB/s
=> the 52x drive is faster than the 60x (this is an exemple)

And as Sunray said, the DVD is using the same kind of "trick", so the DVD transfer rate is normally 1.35MB/s
So a 8x DVD with a 1.35MB rate will have a transfer rate of 10.8MB/s.
So for reading a CD-ROM, the 8x DVD will be faster than the 52x CD.

But I guess that now, most of the X equal the 150KB/s, since the DVD drive.

Hope that can help.
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joey_the_assCommented:
Arl, an 8x DVD-ROM reads DVDs at 10.8MB/s it doesn't read CD-ROMs at that same speed.  It will have a seperate speed rating for CDs, probably 52x which will equal 7.8MB/s
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Valadas2Commented:
Interesting fact:

Several companies have made the maximum speed CD-Writing standard 48x (see article) instead of 52X or higher due to the fact that at 52x the CD is spinning at 10 000RPM and several CDs have been known to explode at those speeds, destroying the drive and some times sending pieces out from the CD tray.

make sure to see this funny link regarding cd explosions: http://www.leenks.com/redirect.php?lid=217
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shaan432Author Commented:

Hi friends,

     If a cd is written in  a certain speed, is it necessary that it should be read and rewrite in same speed.
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grbladesCommented:
No. All that matters is that a CD-R is written to within it rated speed. Therefore if a CD-R is rated at 16X you should not try writing to it at 32X because it may not work. You can read it at any speed you like.
If the drive has difficulty reading the cd because it is scratched or dirty it will automatically slow down anyway.
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DVation191Commented:
I think the author's question was more like, if you burn a CD-R at 52x, does it need to be read at 52x?
The data on the CD-R will be the same, no matter how fast or slow you burn it...likewise, no matter what speed you burn the CD-R at, it can be read at 2x or 52x...it won't matter.
RE-Writing a CD-R generally takes more time than a CD-R, because rewrite speeds are typically slower. But like the above example, the burn speed has no effect on the ability to read at varying speeds
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pjcrooks2000Commented:
X = speed irrespective of what the speed of the device is.  If its a CD Rom and the has a different speed to the DVD then X wlll still always = speed
As i said before x could equal anything as it an angebraic. It could mean x = a dead fish, so that 24x = 24 dead fish.

:)
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pjcrooks2000Commented:
Oooh and on the point of how suitable it it for your system, as long as you have the power to drive it, it will not matter what speed it is.  Except to say if its just 1x then that would be very slow :)  If you have a 300Watt Power supply inside the machine then you will be able to run any drive speed you want.  As long as your not running loads of them at the smae time :)

go for it !  whatever it was you were thinking of buying

pjcrooks2000
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shaan432Author Commented:

 Hi friends,

     I like to clarify one thing. Is  'X' = 150 kilo bits per second or
 150 Kilo bytes per second. Most of u have written that it is kilo bytes per second but  in the site whose link provided by Valadas2, it is given as kilo bits per second. Pls clarify.

Shaan432
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grbladesCommented:
It is kilo bytes per second
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grbladesCommented:
Basically the original drives read at 150 kilo bytes per second because that was the speed required to read a 74 minute CD in 74 minutes and therefore be able to play the audio off it.

When faster drives came out they called it 2X because it read at 300KB/s and therefore twice as fast hence the name '2X'
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grbladesCommented:
This is also why the 'X' represents a different speed when reading DVD media because the DVD specification required drives to read at a much higher speed to play the movie.

P.S You might want to have a look at a DVD instead of a CD drive as the price difference is very little.
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ArlCommented:
Hi,

No doubt, this is KB and not Kb, so Kilo BYTES.
Cause otherwise, 150kbps will be quite slow... very slow, and will take obviously several hours to write at 1x.
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BurbbleCommented:
Yep, kilobytes (technically kibibytes)...

74 minutes * 60 seconds/minute = 4,440 seconds

4,440 seconds * 150 KB/second = 666,000 KB (lucky number)

666,000 KB / 1024 MB/KB = 650.4 MB

Voila :)

-Burbble
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DVation191Commented:
the kilobits site is inaccurate.

just to quote my own above post...
"CD X units are equal to 150 kilo*bytes*/second; 1X is fast enough to write a full 74-minute audio CD in 74 minutes.
DVD X units are equivalent to 1.3 mega*bytes*/second, or enough to write a single DVD in about 60 minutes. "
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