Classic Computer Magazine Archive CREATIVE COMPUTING VOL. 9, NO. 6 / JUNE 1983 / PAGE 114

An alternative to the Atari 810. (Percom Data disk drive) (evaluation) Winston Lawrence.

An Alternative To The Atari 810

Double density 5 1/4 disk drives for the Atari have finally arrived. Percom Data Company is now shipping Ataricompatible disk drives. I ordered one of these drives from my local Percom dealer as soon as I heard the announcement and within a week had one of the first drives in New York.

One of the biggest drawbacks to trying to use the Atari computer for business and serious programming has been the limited storage capacity of the single density 810 disk drives. The single density drive holds about 88,000 bytes (characters) of storage, which does not leave much room for data once programs have been stored on the disk. The double density disk drive from Percom allows approximately 176,000 bytes of storage.

The single unit disk is about 50% heavier than the Atari 810 drive and is encased in a solid metal enclosure. The drive stands about 6 1/2 high, by 4 1/2 wide and 11 deep. Two of these drives take the same amount of desk space as oen 810 drive because the Percom drive is mounted vertically, while the Atari 810 is mounted horizontally.

The Percom drive comes with a manual which explains the installation and checkout of the drive system. My manual was marked Preliminary Copy and several sections were left blank with a notation that the information would be included in a later version.

Nevertheless, the actual installation of the drive was easy, and the manual did explain how to attach the drive to Atari computers with no other drives and to Atari systems with one or more 810 drives. The dirve came with the familiar Atari connector cable and plugged in just like any other peripheral device.

It is important to note, however, that when the Atari system does include 810 drives, the Percom controller drive must be drive number one.

The back of the Percom controller drive has two Atari connectors and a white 34-pin connector. This connector is used when adding additional Percom drives and will be very important in the future. It can be used by the controller to control additional 40-track double density drives, 80-track drives, and even 8 drives.

Only the first Percom drive must have the controller card installed. The controller can then control three additional drives. If you were to add two additional controller drives (each of which controls three add-on drives), you could have an eight-drive system in place of the maximum of four 810 drives.

Additional Percom add-on drives do not require the controller cards, so the cost of an add-on drive is $399--about half the cost of the $799 double density drive with the controller card.

The only hardware problem I have noticed is that the cassette recorder cannot be used with the Percom unit attached. I do not use cassettes very often, so this is not a big problem for me. When I do need it, I boot the disk, then pull the connector out of the computer console I/O port, and plug the cassette recorder in. I unplug the recorder when finished, plug the drive connector back in, and continue.

The Percom drive controller determines whether a disk is single density or double density during the boot process and switches to the correct mode of operation, making it suitable for use in an Atari system even when it is the only drive in the system, as single density disks will cause the drive to operate in single density mode.

Percom supplies a Basic demo program that changes the mode of operation of the unit from double to single density, or from single to double density. Another utility supplied by Percom, BLD, is used to convert the Atari DOS 2.0s to work with double and single density drives. Percom does not supply a DOS with its drives, so the purchaser must get a copy of DOS 2.0s before using the system.

The DOS works the same as the unmodified Atari DOS 2.0s, however, the Percom installation manual notes that the duplicate functions (file or disk) will not work between double density and single density disks. The copy a file or DOS menus can be used to copy a file or an entire disk using the *.* wildcard as file names. The duplicate functions will work if the Percom disk is in single density mode and the disk was formatted in single density mode.

Percom has provided a utility called SDCOPY for users who have only one disk drive. SDCOPY is used to copy (duplicate) disks or files of different densities.

The following steps must be taken to create a double density DOS.

1. Place the DOS 2.0S disk into the Percom drive and boot the system.

2. Replace the DOS disk with the utility disk supplied by Percom and run the BLD utility.

3. Remove the Percom utility disk, insert a blank disk and, using the DOS menu, format this disk.

4. Select the write DOS option from the menu and write the modified DOS back to disk.

You now have a double density disk which can be used only in the Percom drive, but which will allow normal operation with the 810 if you are also using 810 drives.

Percom does not review the DOS installation procedures provided in the Atari DOS 2.0s manual, and you should ensure that the DOS is set up for the correct number of disk drives. I had several 160 errors attempting to use the Percom disk after installation until I realized that I had originally set up my DOS for single drive operation. It is a good idea to reread the Atari DOS manual if problems occur after installing the unit.

The Percom disk drive works and has performed flawlessly over the past six weeks. as a side benefit, it is faster than the Atari 810 drive so that I/O operations to the drive take a noticeably shorter time. Percom has not released any information regarding the internal operation of the drive, but at least one command has been added to the original Atari disk commands.

Percom's drive controller demonstration program shows a 78 (decimal) command which apparently causes the drive to return 12 bytes of information containing the number of tracks in the drive, the number of sectors in a track, and the number of bytes in a sector. This command does not return any useful information when sent to an 810 drive. The other disk commands (PUT SECTOR, PUT SECTOR WITH VERIFY, GET SECTOR, FORMAT DISK, and STATUS) work the same as they do with the 810.

Atari computer owners contemplating the purchase of a first or second disk drive should give serious consideration to the Percom unit. Although the $799 list price is nearly 50% higher than the list price of the 810, double density disks and the capabilitye to control 8 drives make this a serious competitor.

The biggest problem at present is a lack of software to control these new drives and the Atari 810 drives at the same time.

Percom Data Company, 11220 Pagemill Rd., Dallas, TX 75243.

Products: Percom Data Double Density Disk Drive (computer apparatus)