Dinosaur
06-26-2001, 03:18 PM
When I first read that CD data transfers are faster for the outside tracks, I nodded my head and agreed. It is obvious that at a constant rotational speed, more inches or millimeters of CD pass under the head per second. This cannot be the whole story.
The above assumes a constant data density on all tracks. Are CD’s written with variable speed devices that result in the data density per inch or millimeter being constant for all tracks? What is the production process?
It is my understanding that a hard drive runs at constant rpm and gets the same transfer rate on inner and outer tracks. It has a constant rate at which it reads and writes bits of data. This results in fewer bits per inch or millimeter on the outer tracks, because more inches or millimeters pass by in a fixed amount of time during the writing process.
It is my understanding that there is at least one timing track on a hard disk which controls reading and writing on all data tracks. The hard drive manufacturer writes the timing track as part of some formatting process. There after, when a read head sees a signal on the timing track, it writes/reads to/from a data track.
At least the above is my understanding of the way hard disks work. This process results in variable data density but a constant rate of data transfer for inner and outer tracks.
Are CD-R’s and CD-RW’s like hard disks or like ordinary CD’s?
How much of my understanding of hard disks (if any) is correct?
Does anybody at this forum have an in depth understanding of the above? Perhaps an engineer from a disk manufacturer subscribes. That would be nice.
------------------
Gouverneur
Eschew Obfuscation!
If one hundred million people believe a foolish idea, it is still a foolish idea.
The above assumes a constant data density on all tracks. Are CD’s written with variable speed devices that result in the data density per inch or millimeter being constant for all tracks? What is the production process?
It is my understanding that a hard drive runs at constant rpm and gets the same transfer rate on inner and outer tracks. It has a constant rate at which it reads and writes bits of data. This results in fewer bits per inch or millimeter on the outer tracks, because more inches or millimeters pass by in a fixed amount of time during the writing process.
It is my understanding that there is at least one timing track on a hard disk which controls reading and writing on all data tracks. The hard drive manufacturer writes the timing track as part of some formatting process. There after, when a read head sees a signal on the timing track, it writes/reads to/from a data track.
At least the above is my understanding of the way hard disks work. This process results in variable data density but a constant rate of data transfer for inner and outer tracks.
Are CD-R’s and CD-RW’s like hard disks or like ordinary CD’s?
How much of my understanding of hard disks (if any) is correct?
Does anybody at this forum have an in depth understanding of the above? Perhaps an engineer from a disk manufacturer subscribes. That would be nice.
------------------
Gouverneur
Eschew Obfuscation!
If one hundred million people believe a foolish idea, it is still a foolish idea.