24X What>?

[Mr. Mainstream]

wen cd-writers/reader say they rite or read at 24X its reading 24 times what? the speed of sound?

[CCSDUDE]

24x would be 23 (4) times as fast as a 1x CD drive...so just take 150kbs and multiply it.

[Krell]

Theoretically, thats 24 * 150,000k = 3.6 Mb/s thruput to the bus.

That's "theoretically"


edit: ooops that zero was important after all!
thx cpu

[cpugeniusmv]

for CD's:
1x = 150 kbits/sec

for DVD's
1x = 1.35 mbits/sec

[gorphon]

ummm..... even theoretically, correct me if Im wrong krell..... but 52x speed drives only approachthat kind of limit (3.6MB/s) on the very outer ring.... and even then, they dont burn that high. so the logic, though simple, is flawed.

edit: I just remembered a term used in economics: ceteris paribus, "everything else remains the same". and I think thats the way they arrive at the theoretical limit. but the type of media and, as krell has told us, the vibration of the platter (and Im sure some other things I cant think of/dont know about) make a difference in speed. sos the numbers on the burner dont tell you a whole lot more than how fast (in minutes) a burner is likely to burn. and I know there is no way a 24X burner burns a 650meg disc in right around 3 minutes. thats faster than my 32x.....

krell, dont burners have a form of "vbr" (called something else) themselves where they spin (and burn) slower for the center of the disc and faster on the edges?? I seem to remember reading about this with the latest 52x burners....

and companies who dont want to produce media that is that fast because of cd media's tendency to shatter at speeds over 10,000 RPM

[Krell]

Yes they do, but what they SAY they do, and what they actually DO is 2 different stories. Kinda like most people you know.

[narz]

Let me pose this question. How many CDs have "blown up" or been shattered whilst spinning at high speeds. I have never seen it happen, and thus, don't really believe that it happens. The theory sounds as if it MIGHT happen, to maby one person every year by some freak thing, but who really knows? All i know is that my 48X24X48 drive hasn't yet ripped apart a cd.

[gorphon]

thats because you have yet to hit 10,000 rpm while at 48x. now, the fact of the matter is that many of the major cd media manufacturers are wary of 52x media because of its tendency (due to micro small differences in balance throughout the disc I would imagine) to shatter at such high speeds.
does this mean its gonna happen? no, not necessarily, just that it could. and the fact that many of the major manufacturers dont want to produce this media leads me to believe that it happens pretty regularly. BUT (a big but), it has yet to happen to any consumer that you (or I) have heard of because cd burners that write at over 10000 rpm have just recently (within the passt week, to the best of my knowlege) hit the market.

[Theinfamousone]

24x refers to X being real time. So if the CD is 48 minutes, it will burn it at 24 times real time which means it will take 48 minutes/24 = 2 minutes. That is on the outside edge, they go faster as they get to the outside, and yes they do spin slower at the beginning (I don't know if it's called VBR since I thought that just referred to variable bit rate which CDs are always a CBR of 1411-1511 kbps depending on what you set it to and/or the company making them sets it to). Yeah, I'd like to see one blow up, that's pretty dang fast I'll say that. I've ripped CDs so fast that I was wondering if it was going to blow up, my friends and I were thinking that they should put another gear on those drives. It sounded like a jet engine reving up. Anyone have any links of CDs blowing up? That would make good bed time reading.

[gorphon]

its not called VBR... I just used that term to describe what I was talking about as they both vary... one varied bit rate and the other varies speed.... it is just the closest example that I could think of.

hmmm... and now that I think about it, it was the new 56X speed drives that you will not see a lot of media for... and even 52x sees very little to no certified media. gimme a minute and I will find some links.

edit: no pictures, sorry: extremetech article (http://www.extremetech.com/print_article/0,3998,a=32850,00.asp)

and oh, theinfaimousone: thanks for all the links!

[Krell]

http://www.acersupport.com/technical/articles/common/cdrom_speed_dp10204.html


I'm telling you, that 1X = 150Ks ! PERIOD

Read ALL these links
http://www.howstuffworks.com/cd2.htm


THAT has nothing to do with the VBR of a file being decoded in Windows.

ONE is bus speed, thru put.

The OTHER is the decompression of the file.

[gorphon]

Originally posted by Krell
[url]

ONE is bus speed, thru put.

The OTHER is the decompression of the file.


I know that man... it was justt an excample I was using, I had put quotes around the term "vbr" originally to denote that that was not what it was called... I just used it as an example to make it easier to explain what I meant. however, a bad example it obviously was as it seems to have caused much confusion.

[Krell]

Im not talkin about you Gorphon, first of all if it HAD been you, I would have PMed you. Also, you were here thru the "laser" days, so I know you know what youre talking about.

[DainBramaged]

To my knowledge, all the numbers that have been stated are correct. In terms of CD-ROM speed, 1X = 150 kbits/sec. Multiply thusly. In terms of DVD-ROM speed, 1x = 1.35 mbits/sec. Multiply thusly. Of course, these are theoretical numbers, under optimal lab conditions.

The two methods that CD-RW drives currently employ are called Constant Linear Velocity (CLV) and Constant Angular Velocity (CAV). CLV maintains the same write speed at any point of the disc. CAV is what most of the faster writers use. By manipulating the rotation speed of the media, higher writing speed can be attained.