Portable disk unit for NEC 8201. (evaluation) David H. Ahl.

The NEC PC-8231A is a portable single or dual 3-1/2" disk drive unit for the NEC PC-8201 notebook portable computer. The unit can be powered by either a rechargeable battery or AC adapter and provides true portability, assuming you don't mind its arm-stretching weight of 7.8 lbs.

The unit measures 11" x 10.5" x 3" and sports a collapsible carrying handle on the right side. The battery (or AC adapter) fits in a slot on the left side. At over 7" long and with a weight of 1.5 lbs., the 12-volt, 1.5-ampere hour battery is a bit of a monster. Depending on disk accesses, it should have a life of about 1 to 1-1/2 hours, while recharge time is two to three hours. Using the included connector block, the AC adapter doubles as a battery charger.

In operation, the protective front of the disk unit folds down and elevates the drive by about 1-1/2". On the front is a power switch, green LED power indicator, drive door, and red LED drive access indicator. Once the drive had been accessed, it continues to spin for several minutes to speed subsequent accesses. Getting More Storage

At the outset I should point out that we were at a bit of a disadvantage in testing this product, as we had a prototype unit from Japan with no documentation whatsoever.

The disk unit is connected to the computer with an eight-conductor cable with modular telephone-type jacks. After powering up the first time, pressing the reset button on the computer automatically loads the Disk Basic overlays. Once loaded, they are retained in memory unless you turn off the battery backup power. These routines occupy 3035 bytes; thus a 32K machine (which actually has 28758 free bytes) will end up with 25723 free bytes.

Disk operations are available from Basic or the main menu (for text files). To save a text file from the main menu, for example, you would press function key 2. In response to the prompt "Save file.DO as" you would respond, "1:File.DO" and the file would be written to disk. The LOAD and KILL commands are also usable from the main menu.

It took me a good deal of time to determine how to get a disk directory; it turns out the command is FILES (1). Unfortunately, it appears that there is no way to print a directory; hence, if you have more than 12 files (the number of names that fit on the screen), you must read fast as the first ones scroll by.

The system disk contains three programs: Format (formats a blank disk), Backup (creates a backup disk), and Xfies (transfers files from one disk to another). I also had a demo disk with seven additional programs for checking the system and the like; none of these programs are essential to system operation. In fact, I judge them somewhat dangerous since they use many POKES, and at least two of them hung my computer so thoroughly that I needed to cold starting the machine.

A formated data disk has 158 free blocks of 2K each to give it a total storage capacity of 323K. A system disk has a capacity of 307K. These figures are a bit misleading since the system assigns disk space in 2K increments. For example, a 4200-byte program (106 bytes larger than two 2K blocks) requires three blocks (or 6144 bytes) of storage space. Thus, the realistic capacity of a disk is probably more like 250K (which still is a great deal of space compared to the internal memory of the machine).

Using the disk from Basic is quite simple; disk file names are simply preceded by 1:. Other commands that can be used are DSKF(1) (gives free space on disk), DSKO$ (writes data on disk), and DSKI$ (reads data from disk). These latter commands are used in conjunction with the file commands OPEN, CLOSE, and FIELD. Worth the Price?

My only complaints with the 8231 are its arm-stretching weight and its inability to print a file directory. Functionally, it behaved perfectly, and my ability to use it sans instructions is testimony to its ease of use.

If the 8201 is your only computer and you find yourself running out of memory space for long text files or constantly saving programs on cassette tape, the 8231 disk drive will be a most worth-while addition to your system. Also, if most of your travel is by car or if you stay in one spot for a while when traveling, the weight of the drive will not be a major factor and you will want to consider getting one. On the other hand, if you use your 8201 primarily in conjunction with a larger desktop machine, you may find that the $799 price tag on the 8231 means "not worth it for me."

Products: NEC PC-8231A Portable Disk Drive (computer apparatus)