Classic Computer Magazine Archive ANTIC VOL. 7, NO. 2 / JUNE 1988

Atari's New Super Disk Drive

First look inside the XF551


Atari's newest disk drive for the XL/XE line of computers has finally reached the market (although with remarkably little fanfare). The new Atari XF551 carries the same $ 199.95 list price as the good old 1050 drive it is meant to replace. Later this year Atari's newest disk operating system, ADOS by Bill Wilkinson, is supposed to be available. The first shipments of XF551 drives came with Atari DOS 2.5 which, while an adequate earlier Wilkinson-written DOS, doesn't really do justice to the capabilities of this powerful hardware.


Atari XF551 Disk DriveThe XF551 is eerily silent during operation. When I turned it on, I expected something like the "coffee grinder" sounds of the old Atari 810 or the "bear growl" of the 1050. Instead came a brief whirr-- then, nothing. There is often a two-second pause when starting a boot, while the drive determines the density of the disk. Fortunately, the monitor speaker informed me that the system was in fact doing something and shortly the DOS menu appeared.

The XF551 is the same gray color as Atari XE computers. It is considerably smaller than the 1050--about 2 3/4 x 7 1/4 x 11 1/2 inches--and weighs in at six pounds. A tiny green "busy" light is just to the left of the door lever. Setting the drive number is done with a tiny pair of switches- similar to printer DIP switches which protrude slightly from the rear cover. The top of the cabinet has two rows of vents for cooling.

The power switch has been moved to the right rear corner of the cabinet and there's no pilot light on the front panel. (I left my XF551 turned on for days because of this-with no apparent damage.) While on standby, the XF551 uses about as much power as two night-lights. It uses the same external power supply as the 810 and 1050 and has the usual two Atari nonstandard serial ports for daisychaining.

Inside (yes, I voided my warranty), we find a 6507 microprocessor, a drive controller chip, a DC power supply and a drive mechanism with industry-standard power and controller connections! Visions of slipping in a 3.5 inch microfloppy danced before my eyes when I saw this. (An article by Robert Woolley in theJanuary 1988 San Leandro Computer Club journal discusses how to do this.-ANTIC ED)

Atari DOS 2.0 and 2.5 work as you'd expect with a 1050-single or enhanced density, 90K or 130K of storage, etc. But wait! Side B of my "flippy" wouldn't format. Some investigation revealed that although I could boot and load from the back side of a disk, just as with a 1050, the XF551 won't format or write to it because the index hole (the small hole near the center of the disk) was now on the wrong side.

DOS XL from ICD/OSS, SuperDOS (reviewed in this issue) and SmartDOS can all format single-sided, double-density disks in the XF551. However, DOS XL took a lot of coaxing and I still have trouble duplicating the exact steps required to do it. Even more frustrating is the fact that DOS XL's CONFIG utility tells me that the XF551 has two sides, but the DOS XL command processor only allows access to 180K.


Most of the software I own, including Speedscript 3.0 and the Antic Spell Checker, worked normally when transferred to a double-sided, double-density disk. Some programs will do strange things if you try to format a disk or get a directory when using any DOS not found on the original disks. Turbo BASIC works exactly as it should in all densities.

The only way to be sure if a specific program will work properly on a double-sided, double-density disk is to try it. My system has an 810 installed as drive 2 and the XF551 is drive 1. The only problems I encountered arose from trying to change densities within an application such as a word processor or spreadsheet, or from using a copy-protected program under a different DOS.


The XF551 isn't much faster than the 1050, using the operating systems currently available. The forthcoming ADOS is promised to support rapid, interlaced formatting and high-speed loads and saves. Since ADOS isn't available at this time, I ran some tests with SmartDOS (Astra Systems) to compare the three Atari drives. (See Figure 1.)

The times in this test were determined using the system clock. All files were written to and read from the same disk, using the same filename. The files were deleted before testing another drive, and the same computer was used each time.

Some quick figuring reveals that on a standard 62-sector picture file (8K), the XF551 is about 23% faster than the 810 and about 12.5 % faster than the 1050. For longer files, the improvement over the 810 increases, achieving a 60% advantage at 32K during a write-without-verify operation. However, I found that the gap between the XF551 and the 1050 actually decreased with larger files.

Drve Type
Format SS/SD
Write 8K File Verify ON
Write 8K File Verify Off
Read 8K File
Write 32K File Verify ON
Write 32K File Verify OFF
Read 32K File


Here are a couple of things to watch out for, as you enter the contemporary world of double-sided disk drives:

1. Always put the cardboard head protector in the drive and close the door before moving the XF551. Double-sided drives are considerably more sensitive to shock and vibration damage than the 1050 and 810 .

2. Never remove a disk while the busy light is on. This is especially true with double-density disks. While it may not damage the disk and won't hurt the drive, sometimes you won't be able to access a double-sided, double-density disk again without rebooting the system. One possible alternative is to always boot from a single-density copy of your DOS disk, then use the DOS Menu to reconfigure the drive. With any luck, if you need to re-enter DOS after an unintentional density change, this method will make it possible.

The XF551 is a modern, rugged drive that delivers good value and reliable operation. I can recommend it without hesitation to any Atari 8-bit owner who wants economical price and compatibility with stan- dards already established.

Rich Tietjens is a US. Army Staff Sergeant stationed in Europe, where he made his early XF551 purchase.

Atari Corp.
1196 Borregas Avenue
Sunnyvale, CA 94086
(408) 745-2000