Dosplus and D

An operating system that makes compatibility easy

Model I/III

Captain Paul M. Hine, San Diego, CA

The TRS-80 Model I owner can easily lay claim to a wider choice of operating systems and hardware configurations than for any computer system since the IBM System 360. The choices vary from the simple (TRSDOS 2.3 and OS-8O) to the very complete (NEWDOS/8O version 2.0 from the folks at Apparat). In between have been the excellent products from LOBO and Microsystems Software, as well as NEWDOS-PLUS.

In their current offering, Microsystems Software has made worthwhile revisions to DOSPLUS 3.3, with enhancements to both the DOS and BASIC language portions of the package. The most marked change has been in documentation, which is now competitive with that offered by the finest software houses in the microcomputer support business. The least apparent change is one of adaptability to other systems designed to support hard disk systems on the TRS-80. Compatibility to eight inch floppy drives is also included if the system is configured with an appropriate drive controller.

I reviewed this new operating system using a Model I TRS-80 with an LNW expansion board, LNDOUBLER (to attain double density operation), and three disk drives. Drive zero was a 40-track (MPI B51), and both of the other drives were 80-track units (also MPI). Although DOSPLUS supports lower case modifications and automatically senses this installation, I didn't have one installed. A speedup installation can also be installed and the DOS will manage it to avoid I/O incompatibility.

All three drives were operated at six millisecond track stepping, and the 80-track drives were operated both as 80-track units and, with novel "track skipping", as 40-track drives.

Three distinct grades of floppys were used and the results were locked out during formatting. On premium floppys, no granule lockouts occurred, proving that for 80-track, double density operation, you get pretty much what you pay for. During 75 hours of operation, three CRC errors happened, and all of these were on the economy floppys. This was cured by using the verify mode of DOSPLUS, which fought through the lower grade floppys without further lost data.

Earlier versions of DOSPLUS gained a reputation for reliability, ease of use and poor documentation. The whole documentation issue can be put to bed right away. The user's manual provided with DOSPLUS 3.4/4.0 is handsome, well written, well organized and readablel Some reference to Radio Shack's TRSDOS manual may be advisable, so don't throw that away if you purchase DOSPLUS. The assembly language buffs will be delighted with documentation for many calls to DOSPLUS routines. Some of these are understandable and handy for us BASIC language types to modify our little machine language modules and monitors. The printer driver is flexible enough to handle just about any ASCII serial or parallel printer, and even does the graphics conversions for EPSON owners. This DOS can do nearly anything the others can, including:

1) Formatting from 20 to 96 cylinders (new word for trade) on any drive in either single or double density.

2) Double stepping an 80-track drive to produce or read a 35- or 40-track floppy (you can change it back and forth by command from a BASIC program if you need to change disks).

3) Using any drive as either a double density or single density drive without making any changes in "system" or configuration files. Just put the disk in the drive and DOSPLUS selects the appropriate controller chip to run the show. Files from single density TRSDOS formatted disks can be "copied" directly to double density disks and vice versa!

Format is one of the long suits offered by DOSPLUS. During the format of cylinders (called that for compatibility of terminology with the dual-headed and hard disk crowd), the head is stepped toward the center as in TRSDOS and NEWDOS/80. When the innermost track is reached, the verification is done from inside-out. Aside from being quicker than TRSDOS or NEWDOS, this technique looks for excessive radial error due to hystersis in the drive's stepper. (Hystersis is the slop in a leadscrew or band positioner. That is bad news, particularly on 80-track drives.)

If the format operation verifies, and the system is operated in the Verify mode (read and verify after each write), you can be assured of good data reliability. Where December, 1982 57

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