Disk IO caching?

Discussions on more advanced topics such as monolithic vs micro-kernels, transactional memory models, and paging vs segmentation should go here. Use this forum to expand and improve the wiki!
User avatar
Brynet-Inc
Member
Member
Posts: 2426
Joined: Tue Oct 17, 2006 9:29 pm
Libera.chat IRC: brynet
Location: Canada
Contact:

Re: Disk IO caching?

Post by Brynet-Inc »

I don't know.. many blank disks (..or discs) include both a data capacity and a time capacity.. (700M, 80mins).

I've burnt music (..yes, illegally) on such disks, not mp3 files.. actual audio disks.. so if there was at one time 2 different types of disks, they're hybridized now.
Image
Twitter: @canadianbryan. Award by smcerm, I stole it. Original was larger.
quok
Member
Member
Posts: 490
Joined: Wed Oct 18, 2006 10:43 pm
Location: Kansas City, KS, USA

Re: Disk IO caching?

Post by quok »

JackScott wrote:<$0.02>
While I'm not confident either way, what bewing says does make sense in that I can remember back in the day when your old audio CD players couldn't play CD-Rs. My portable CD player doesn't read CD-RWs. Just anecdotal evidence, but it would make sense.

Although, it could have something to do with the reflective chemicals used?
</$0.02>
The problem is not such much the reflective chemicals being used so much as incorrect wavelengths being used by the CD's laser.

The "MultiRead Specification", by the Optical Storage Technology Association, answers a lot of this. It says there are four types of CD media: CD-DA, CD-ROM, CD-R, and CD-RW. CD-DA and CD-ROM both use the same laser wavelength to be read. CD-R and CD-RW, aside from using different reflective chemicals, also use different laser wavelengths. The same goes for DVD-RAM, DVD+-RW, and DVD+-R. DVDs also have DVD-Audio and DVD-ROM media types. The MultiRead specification addresses CD and DVD media types, and ensures that MultiRead compatible drives can access all types of media. Of course, this doesn't allow a CD drive to read a DVD, but it does make sure that DVD drives can read all four types of CD media. All drives today should be MultiRead compatible.

The MultiRead Specification is largely meant for computing devices. There is also the MultiPlay Specification, which presents the same kind of information as the MultiRead Specification, but is meant to ensure that DVDs (and CDs) recorded by a computer can be played in a stand-alone DVD (or CD) player.

What JackScott is referring to above would be the MultiPlay Specification.
skyking
Member
Member
Posts: 174
Joined: Sun Jan 06, 2008 8:41 am

Re: Disk IO caching?

Post by skyking »

bewing wrote:I've been a (tiny) computer store owner for 12 years, and my info comes directly from my recordable media distributor (Horizon USA). So I'm willing to directly challenge wikipedia on this one. There are both "audio" and "data" blank CDs, they are different, and the difference is helical vs circular tracks.
But isn't this what sales people is supposed to say? You wouldn't expect them to say that Audio CD's are the same but a lot more expensive.

For the claimed difference a ordinary CD-player would not be able to play a data CD since it would need to have higher rotation speed in order to be able to make up for the cylinder-to-cylinder seek time. There would also need to be extra data indicating where the cylinder begins which is not needed if the groove is spiral. To me it seems that changing the format would break the compatibility.
earlz
Member
Member
Posts: 1546
Joined: Thu Jul 07, 2005 11:00 pm
Contact:

Re: Disk IO caching?

Post by earlz »

bewing wrote:I've been a (tiny) computer store owner for 12 years, and my info comes directly from my recordable media distributor (Horizon USA). So I'm willing to directly challenge wikipedia on this one. There are both "audio" and "data" blank CDs, they are different, and the difference is helical vs circular tracks.
could this explain why really old CD players(the first ones?) didn't work with CD-Rs
jal
Member
Member
Posts: 1385
Joined: Wed Oct 31, 2007 9:09 am

Re: Disk IO caching?

Post by jal »

earlz wrote:could this explain why really old CD players(the first ones?) didn't work with CD-Rs
Read the whole thread before replying :).


JAL
earlz
Member
Member
Posts: 1546
Joined: Thu Jul 07, 2005 11:00 pm
Contact:

Re: Disk IO caching?

Post by earlz »

jal wrote:
earlz wrote:could this explain why really old CD players(the first ones?) didn't work with CD-Rs
Read the whole thread before replying :).


JAL
my bad.. lol..

btw, as of this moment I am one post behind you rofl
User avatar
Love4Boobies
Member
Member
Posts: 2111
Joined: Fri Mar 07, 2008 5:36 pm
Location: Bucharest, Romania

Re: Disk IO caching?

Post by Love4Boobies »

Omg! :shock: No one mentioned different algorithms and avoiding starvation?
"Computers in the future may weigh no more than 1.5 tons.", Popular Mechanics (1949)
[ Project UDI ]
Post Reply