Classic Computer Magazine Archive COMPUTE! ISSUE 90 / NOVEMBER 1987 / PAGE 71


Bill Wilkinson

Atari's Newest Drive

After three months of pretty heavy stuff, it's time for a slightly different tack. And since my time has recently been monopolized by a project near and dear to all eight-bit Atari owners, I've decided to share some "secrets" with you. We're going to take a very close look at the new XF551 drive from Atari.

The XF551 is a sleek drive, lower and wider than a 1050, and in a style and color that matches the XE computers. Quite simply, it looks good. As you read about the internals of the drive, I hope I can convince you that Atari has really done something right.

The XF551 started out as the XF351—the 3 designated a 31/2-inch drive. Some people are disappointed that Atari changed over to a 51/4-inch drive, but I view it as a very positive step. Current users can upgrade to this drive, yet still keep and use all their old disks. Software manufacturers don't have to produce two different versions of their software, and there are other points of compatibility.

For starters, the drive is compatible with disks created by virtually all Atari-compatible drives—in single, enhanced, and double density. Not only that, several of the different DOS systems I've tried have also worked flawlessly. And I know Atari has tested the drive with many, many pieces of commercial software with many different protection schemes. Summary: The drive works, and works well.

At a suggested price of under $200, the very fact that a true double-density drive is now available from Atari would be welcome news. But the drive is also double sided. That means that each disk can hold up to 360K—nearly three times the capacity of a 1050 and four times that of an 810.

As I write this article, Atari does not have a DOS that will support this extra capacity. However, the reason this drive has monopolized my time recently is simple—I have been writing a new DOS for Atari. ADOS (as it will be known) is full-featured, with subdirectories, random access files, a combination menu/command structure, and much more. However, it is not releasable as I write this, so back to the drive.

Inside The Drive

As you may remember, I discussed SIO (Serial Input Output) as it applies to disk drives, in the September 1985 issue. I noted that the four basic SIO commands are R,W,P, and S, for Read, Write, Put, and Status, respectively. Besides these, the Atari 810 and 1050 only understand format commands.

Then, in the next issue, I explained the concept of a device configuration table, as implemented by all the makers of true double-density drives. Well, we can add Atari Corporation to that list: The XF551 supports the Percom standard configuration table. That means you can tell the drive that it's an 810, a 1050, a double-density drive, or (best of all) a double-sided double-density drive. Or, perhaps just as important, the drive can tell you what kind of disk it holds. For these capabilities, we add N and O (which I think of as iN and Out) commands on the serial bus.

But there's even more. If you send it a Read or Write or Put command with the upper bit set (the inverse video bit, in screen terms), then the XF551 transfers data in high-speed mode. To take advantage of this, you need a compatible DOS, but ADOS is nearly ready and I'm sure others will be modified to support high-speed transfers.

Last, but not least, the XF551 adds a special format command (hex $A1, an inverse-video exclamationpoint) that tells the drive to use a special high-speed interleave that enhances the high-speed read and write commands even more. (But note that ordinary reads and writes are even slower than usual on disks formatted in this special way, just as they are on Sparta DOS ultraskew disks used in non-US Doubler drives. I should warn you that each of these drives seems to use a slightly different high-speed scheme.)

So the drive gets my nod of approval from a software standpoint. But what about the hardware? Will the drive stand up to physical abuse, overheating, and the like? Truthfully, I have not had even the prototype long enough to make a definitive statement on this point. But I have had the cover off the drive, and I have looked at its construction. It looks great. The inside is as well built as the outside.

In fact, Atari has never produced a more solid piece of equipment. The drive frame is heavyduty cast aluminum, the mechanical parts are finely polished and aligned, and the controller board appears to be adequately ventilated. Only one point of caution: Double-headed drives are more sensitive to shock and misalignment than their single-headed cousins. Treat the drive with care. Always use its cardboard protector when you move it. Make sure it has adequate ventilation. In other words, use common sense.

If this column sounds like an advertisement for the XF551, I won't apologize—I'm not getting a penny in royalties on the drive or ADOS. This glowing report is for one reason and one reason only: I just had to tell you that Atari has not abandoned the eight-bit market. And they've proven that fact in grand style.