Diff between 650 MB and 700 MB CD ROM

  • Thread starter Thread starter Roedy Green
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Roedy Green

I wondered what the physical difference is between a 650 and 700 MB
recordable CD ROM.

How does the drive figure out which kind of blank it has? What does
it do different to record?

I have heard audio cds created this way are compatible with home
units. Is it just they allow more inner tracks of recordable surface?
 
A 700 MB CD records farther towards the outer edge than a 650 MB CD. Most software and hardware will attempt to record up to 700 MB regardless of the media. I have a 5 year old CDRW with software almost as old that records 700 MB with not problem.
 
A 700 MB CD records farther towards the outer edge than a 650 MB CD. Most software and hardware will attempt to record up to 700 MB regardless of the media. I have a 5 year old CDRW with software almost as old that records 700 MB with not problem.
Click to expand...

The drive just tries to write to the edge, the way it finds out it
can't is if verify fails. The drive can't tell at the start if it has
a 700 MB disk, right?
 
The drive just tries to write to the edge, the way it finds out it
can't is if verify fails. The drive can't tell at the start if it has
a 700 MB disk, right?
Click to expand...

Media information such as capacity, manufacture, and speed information are
incoded so that the drive can read them on a CD/R or CD/RW. From that it
can (usually) tell the fastest burn speed, the laser intensity, and the
capacity of the media. It can usually tell if it is a 650 or 700, but some
drives ignore that.

JT
 
A 700 MB CD records farther towards the outer edge than a 650 MB CD.
Most software and hardware will attempt to record up to 700 MB
regardless of the media. I have a 5 year old CDRW with software almost
as old that records 700 MB with not problem.
Click to expand...


Either capacity of disc can be recordeded further towards the edge to
get a bit more data on the disc, but the 700MB disc has a physically
narrower groove which allows it to be longer (more revolutions) with
roughly the same physical space taken on the media.


Dave
 
A CD writer does not verify automatically. There could be mechanical limitations to how far out the laser can be driven. I have not had a problem with recorders but I have an audio CD player that can't play the last 2 or 3 minutes of a 80 minute CD.
I don't know if a recorder can detect the rated capacity of media. I don't remember trying to record more than 650 MB before 700 MB media came out.
 
A CD writer does not verify automatically. There could be mechanical limitations to how far out the laser can be driven. I have not had a problem with recorders but I have an audio CD player that can't play the last 2 or 3 minutes of a 80 minute CD.
I don't know if a recorder can detect the rated capacity of media. I don't remember trying to record more than 650 MB before 700 MB media came out.
Click to expand...

The recorder MUST detect the capacity, it is a necessary function and
included on all CDRs.


Dave
 
Either capacity of disc can be recordeded further towards the edge to
get a bit more data on the disc, but the 700MB disc has a physically
narrower groove which allows it to be longer (more revolutions) with
roughly the same physical space taken on the media.
Click to expand...

The disc just has a finer grain, and it is up to the burner to put the
tracks closer together.

Seems like remarkable foresight on their part to encode this in a
standard way. How long did it take the film people to start encoding
the ASA with a binary code?
 
The disc just has a finer grain, and it is up to the burner to put the
tracks closer together.

Seems like remarkable foresight on their part to encode this in a
standard way. How long did it take the film people to start encoding
the ASA with a binary code?
Click to expand...

Grain? No, the disc has a groove "width" that determines this.
Narrower goove means more revolutions around the disc, more data
within same physical diameter.
The drive CANNOT decide this but must burn according to the groove
which is used for "head" placement. The only thing the drive can do
is burn past the point which would be the labeled capacity, going
further and futher out towards the edge of the disc until it can no
longer track it's position.


Dave
 
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