CDROM tech - Multi-Level 80mm versus 120mm

[MadRat]

The ML (Multi-Level) technology will give huge increases in storage capacities of a CDROM, going from 660mb to 2GB. But I noticed that articles on ML technology seem to point towards a 120mm CDROM. I imagine if the 120mm disk is 225% the surface area of the 80mm platter then we should end up with a little over 4GB on one of those platters. (Can't imagine anyone would move to this larger platter, though. I'm guessing that a 120mm device would be too wide for a 5.25" bay.)

Does anyone have more information on the ML-CDR's themselves?

 

[highwire]

I took a CD-R off the pile and measured it. It was a little less than 4.75" or 120mm. So I assume 120mm is the size of a regular CD disk.

I know DVD's are often multi-level, but haven't read anything on a ML-cdr yet.

 

[RaynorWolfcastle]

errrr... 120 mm is 12 cm --> 12 cm / 2.54 cm/in. = 4.72 in. There's plenty of space to fit one of those in a 5.25" drive. Highwire is right, I think it is standard CD size...

The thing is, take 700 MB and make it 3 layers and you get ~2.1 GB. Maybe the 2nd and 3rd can't be as dense as the first one but still, you get the idea....


OTOH, area of the disc = outer diameter - inner diameter so...
(6 cm)^2 * Pi - (2.25 cm)^2*Pi = ±97 cm^2
(4 cm)^2 * Pi - (2.25 cm)^2*Pi = ±34 cm^2

So, all else being equal, with a 3 layer, 8 cm disc you get approx. the same usable quantity of information as a regular 12 cm CD


-Ice