Atari Versus Commodore Disk Drives

I read in a lot of articles that the Atari disk drive is an intelligent drive like the Commodore 1541. But isn't it true that you have to load the disk operating system (DOS) into the Atari before it can use the disk drive, whereas the 1541 has DOS built in? Do you really think this qualifies the Atari as an intelligent drive?

Jerry Cole

Good question. An intelligent peripheral is merely one with its own microprocessor, making it a kind of computer in its own right. Intelligent modems can dial phone numbers automatically. Most printers are intelligent peripherals. Years ago, a printer couldn't even print characters on its own. The computer had to turn the daisywheel, strike the character, advance the carriage, and perform linefeeds by commanding the slave circuitry in the printer. Other "dumb" peripherals include the cassette drive, simple modems, and most joystick-type controllers. The television screen could be considered a dumb peripheral. Some computers use one smart drive with a controller, then add unintelligent slave drives which depend on the smart drive.

There's no question that the 1541 is more intelligent than the Atari drive. The 1541 does all disk operations on its own. The VIC or 64 merely has to give some commands. The original Commodore PET was not able to access the disk on its own, so a RAM-loaded DOS was impossible, forcing Commodore to put the DOS in its 4040 disk drive along with the extra RAM and ROM required to support the DOS in the drive. It was necessary to carry over this technique to the 1541 in order to preserve compatibility with PET/CBM 4040 disks.

The Atari 810 (or the new 1050) drive can only read sectors, write sectors, and format disks on its own. Nonetheless, there are real advantages to controlling the drive from the computer. If there is ever a bug in DOS, it's much easier to re-issue a new version of DOS than to have to replace ROM chips in the drive itself. It's also easier to customize and modify DOS when it's in RAM. When the computer controls primitive disk access, far more flexibility and even greater speed is possible. For example, on the 1541, disk errors must be requested from the drive, so it's easy to miss the blinking light, then later find your program wasn't saved. On the Atari, disk errors are tied right into BASIC.

On the other hand, no computer memory is used up when a 1541 is added to a VIC or 64, which is a vital consideration for a 5K VIC. The only real disadvantage of a RAM-loaded DOS is that some memory is made unavailable for other programming.