TRS-80.org » Percom

The Percom PHD

Matthew Reed — Mon, 18 May 2009 14:44:32 +0000

The Percom PHD was a line of 5¼″ Winchester hard drives sold by Percom Data for the TRS-80 Model III, as well as several other computers. Introduced by Percom in 1982, the PHD used what was described as a “smart microprocessor-based drive controller” to allow up to four PHD drives to be connected to the Model III at one time. The Model III version also worked with the Model 4, but Percom never sold a version for the Model I.

The PHD drives were available in 5, 10, 15, and 30 megabyte sizes. The model numbers corresponded to the drive capacity: the PHD-10 was a ten megabyte drive. The prices started at $2495 and increased with drive size.

The Percom Doubler

Matthew Reed — Thu, 12 Mar 2009 14:49:37 +0000

The Percom Doubler was the first successful double-density add-on for the TRS-80 Model I. It was introduced in 1980 by Percom Data Company for an initial price of $219.95. The Doubler hardware was designed by Wayne Smith and Harold Mauch (president of Percom) and the accompanying software was written by Jim Stutsman.

The Percom Separator

Matthew Reed — Tue, 16 Dec 2008 17:26:36 +0000

The Radio Shack Expansion Interface added single-density floppy disk support to the TRS-80 Model I. Floppy disks were a great improvement over cassettes. But many people reported problems with reliability, particularly when reading or writing lower disk tracks. CRC errors and locked out tracks occurred with disturbing regularity.

The Separator, sold by Percom for $29.95, fixed all of those problems. It provided a data separator with far higher resolution (16 MHz) than the separator used by the Expansion Interface (1 MHz). Good data separation was vital for isolating the clock and data pulses that made up a disk track.

Electric Crayon

Matthew Reed — Mon, 08 Dec 2008 15:47:18 +0000

Back in the late 1970’s, the Apple II and the TRS-80 Model I were fierce competitors for computer sales. One advantage the Apple II had over the Model I was the ability to display color graphics. The first product to address this perceived Model I deficiency was the Percom Electric Crayon. Percom introduced the Electric Crayon in December 1979 for a base price of $249. It was featured on the cover of the January 1981 issue of 80 Microcomputing.

The Electric Crayon was a small (12 inch wide by 9 inch deep) box which output a composite video signal that could drive either a monitor or a television set. It connected directly to the TRS-80 printer port and was controlled using EGOS, a ROM-based operating system. EGOS was directly programmed using single character commands. Unique among TRS-80 color add-ons, the Electric Crayon did not use the TMS9918 graphics chip and did not support sprites.

An Interview with Jim Stutsman

Matthew Reed — Thu, 09 Oct 2008 17:32:26 +0000

I recently had the opportunity to interview Jim Stutsman, whose works include MICRODOS and DBLDOS for Percom and Monte’s Windows for Montezuma Micro. In the interview, conducted in October 2008, he had some very interesting answers to my questions and provided some fascinating insight into the early days of the TRS-80.

MICRODOS

Matthew Reed — Mon, 06 Oct 2008 16:53:11 +0000

MICRODOS, later known as OS-80, was the only TRS-80 disk operating system that made no attempt at TRSDOS compatibility. It was written by James W. Stutsman and released by Percom in 1979. Rather than using a command shell like Model I TRSDOS, MICRODOS used extensions to BASIC. It implemented most of the Disk BASIC commands added by TRSDOS. Also unlike the other operating systems, MICRODOS had no file system. All disk accesses were made using the starting sector and length. As stated in the manual: