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Undercolor/850106/Off Color Compact Discs

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UnderColor, Volume 1, Number 6, March 8, 1985

  • Title: Off Color Compact Discs
  • Author: Stephen P. Allen
  • Synopsis: A new technology.
  • Page Scans: Link


The Color Computer is a powerful machine that does some pretty fancy things, but let's face it—when it comes to digital sound, even with four-part harmony the CoCo is in the minor leagues compared to the latest in dedicated digital audio equipment.

I've had a Compact Disc Player for about two months now; I can confidently tell you that digital sound is everything it's cracked up to be. (Now I'm trying to save enough to beef up the rest of my stereo system so my neighbors can enjoy it, too!)

Apart from its astonishing music capabilities (96dB S/N, inaudible flutter and distortion) the CD presents a great potential as a ROM for microcomputers. Consider:

Each second of sound in a CD represents two stereo tracks, each comprising 44.1 K 16-bit words. This works out to 176.4K 8-bit bytes each second. If you were to dump the equivalent amount of memory to your printer at the rate of 40 bytes per line with 66 lines per page, it would take almost 67 pages to represent one second of CD audio! The theoretical storage limit for CDs is 74 minutes—a fully loaded disc could hold over 780 Megabytes of computer data!

As it happens, a standard format exists for computer storage on Compact Disc. It's called CD-ROM, and it's being developed right now. Offering 333,000 sectors of 2048 bytes each, the maximum data storage potential of a formatted disc approaches 682 Megabytes. Here's the breakdown for a sector:


Synch 12 bytes

Header 4 bytes

User Data 2048 bytes

Aux. Data 288 bytes

The Auxiliary Data field is used for extensive error-detection and correction. Current plans call for two levels of error-detection. The first would be low-level (one bit in 10 billion).

This is compatible with current home players. A second, higher level would require circuitry not found in the home CD player, but would detect errors at a bit rate between 10^-16 and 10^-17, which approaches the theoretical limit of error-detection.

With so much storage available the question becomes, "What would be stored?" This may be the most difficult question to answer. Information changes rapidly these days, and the cost of CD production is still high enough that there aren't many reasonable microcomputer applications. (Face it, would you rather have the Encyclopedia Britannica on your computer monitor or in books?)

One possibility suggested is for microcomputer programs. Putting out a program disc with versions for all compatible computers would be a snap. (And when the software has to be updated or otherwise patched, of course the customer would pay. Ah, well . . .)

Industrial uses are easier to envision. How about the master catalog of General Motors Parts? With every part ever made by GM and subsidiaries? With full graphics? The only problem would be getting someone to compile the beast. How about a very comprehensive Intelligent Law Library complete with database management program?

Sony has just announced its lowest-priced CD player yet: about $210 suggested retail. This is as cheap as a floppy drive, and brings an absolutely stunning technology even closer to the ill-heeled computer or audio hobbyist.

Actually, the technology that has a greater possibility for home computers might be the Digital Audio Cassette. Clever engineers are working on the miniature helical-scan tape head; I’m confident that it's only a matter of time.

And so, the computer revolution continues. Just when you think you’ve got the situation pretty well doped out, along comes another breakthrough and it's time to sit up and think again .... Meanwhile, Franck's Second Symphony (or Schubert's Ninth or Steps Ahead) sounds glorious when translated from ones and zeros. (end)