Why do some CD-R suppliers indicate different disk capacities?
The are only two standards, 63 minutes and 74 minutes. You can translate time into data by multiplying the CD delivery rate of 75 blocks per second and 60 seconds per minute. Given each block can contain 2,048 bytes, a disk contains 333,000 blocks which is 681,984,000 bytes. This translates to 650 MB if one divides by 1,024 twice to convert to MB. Likewise, the 63-minute disk holds 283,500 blocks or 580,608,000 bytes which is approximately 550 MB using the same calculation. If it were KBytes the convention is for K to be 1,024 and for k to be 1,000. Unfortunately the convention of capitalized letters does not apply to numeric one million, or 1,000,000 and a binary one million, or 1,048,576. This probably started when disk drives were small and disk drive manufacturers wanted a legal way to make their drives sound larger. You will also see a disc capacity rated as 780 MB, this refers to how much digital audio data can be carried on the disk. Because audio disks require less error correc
