3 ms·

so it's 7.2MB/sec if your data is stored near the edge? Or is data stored "closer together" when it's in the inner track?

bityard 4y ago
With the drive spinning at a particular constant RPM (which is what they do), then the data rate is the same no matter where you are reading the disc.
- IndySun 4y ago
  Nope. They don't (spin at a constant rpm). Perhaps that's not so surprising; after all, it's not vinyl. Furthermore, varying rpm is explicitly mentioned in the headline post. Also explained here... https://www.repairfaq.org/REPAIR/F_cdfaq5.html https://www.repairfaq.org/REPAIR/F_cdfaq5.html
  - jasomill 4y ago
    While the CD data format is defined in terms of constant linear velocity[1], and CD data is always written at a fixed linear density (plus or minus a small margin of error), some drives are, under ideal conditions, capable of both reading and writing this format in CAV mode, as addressed briefly in the "Writing Modes" section of the linked article, http://www.osta.org/technology/pdf/cdr_cdrw.pdf#page=15 http://www.osta.org/technology/pdf/cdr_cdrw.pdf#page=15 In CAV modes, data rate — and laser power, in the case of writing — is a constantly increasing function of the radial position of the read/write head. [1] Though this fixed velocity — and, by extension, data density — is allowed to vary from disc to disc. Assuming the standard (4.3218 Mbit/s raw) data rate, any velocity between 1.2 m/s and 1.4 m/s is permitted, but must then remain fixed within IIRC, a +/- 0.01 m/s margin of error.
userbinator 4y ago
The format is CLV, but drives advertise their speed as the CAV rate at the outer edge where it's the highest, and all high-speed drives use physical CAV so the data rate changes, starting at the lowest at the inner part of the disc where the data begins, and increasing with increasing LBA up to the highest at the outer edge.
aidenn0 4y ago
Yes, you've got it right; the data stored near the center is read at a slower rate (because there is less data on the innermost rings, but most drives spin at a constant speed when not playing CD audio).

bityard 4y ago

With the drive spinning at a particular constant RPM (which is what they do), then the data rate is the same no matter where you are reading the disc.

IndySun 4y ago
Nope. They don't (spin at a constant rpm). Perhaps that's not so surprising; after all, it's not vinyl. Furthermore, varying rpm is explicitly mentioned in the headline post. Also explained here... https://www.repairfaq.org/REPAIR/F_cdfaq5.html https://www.repairfaq.org/REPAIR/F_cdfaq5.html
- jasomill 4y ago
  While the CD data format is defined in terms of constant linear velocity[1], and CD data is always written at a fixed linear density (plus or minus a small margin of error), some drives are, under ideal conditions, capable of both reading and writing this format in CAV mode, as addressed briefly in the "Writing Modes" section of the linked article, http://www.osta.org/technology/pdf/cdr_cdrw.pdf#page=15 http://www.osta.org/technology/pdf/cdr_cdrw.pdf#page=15 In CAV modes, data rate — and laser power, in the case of writing — is a constantly increasing function of the radial position of the read/write head. [1] Though this fixed velocity — and, by extension, data density — is allowed to vary from disc to disc. Assuming the standard (4.3218 Mbit/s raw) data rate, any velocity between 1.2 m/s and 1.4 m/s is permitted, but must then remain fixed within IIRC, a +/- 0.01 m/s margin of error.

userbinator 4y ago

The format is CLV, but drives advertise their speed as the CAV rate at the outer edge where it's the highest, and all high-speed drives use physical CAV so the data rate changes, starting at the lowest at the inner part of the disc where the data begins, and increasing with increasing LBA up to the highest at the outer edge.

aidenn0 4y ago

Yes, you've got it right; the data stored near the center is read at a slower rate (because there is less data on the innermost rings, but most drives spin at a constant speed when not playing CD audio).