The Durango F-85 Computer


In late 1976, George Comstock, who was one of the founders of the daisy-wheel printer manufacturer Diablo Systems, left Diablo after it was purchased by Xerox and started Durango Systems on Bubb Road in Cupertino, California, across the street from another startup, Apple Computer. (We figured that the kids over at Apple would never make it with their underpowered little box).

Comstock's goal was to produce a business computer system constructed around the then fairly-new microprocessor to compete with minicomputer systems which were commanding a significant market share.

From the start, the plan was to create a multi-user system that could run the same applications as the more popular minis. Licensing was obtained from Mini Computer Business Associates (MCBA) for the source for Accounts Receivable, Accounts Payable, Inventory, Payroll and General Ledger applications.

The Hardware

The computer itself was designed using the Intel 8085 CPU and incorporated a self-contained dot matrix printer that could print on standard 14" tractor-feed forms. The system also contained two high-capacity 5.25" diskette drives storing an amazing 480 Kbytes on each single-sided diskette using group code recording (GCR).

A 9" display was positioned over the floppy drives and could display either 64 characters per row by 16 rows or 80 characters per row by 24 rows using the Intel 8275 display controller. (Intel VP Bill Davidow was on Durango's board of directors, so Intel tended to be very responsive to our requests.) Available options included a four serial port interface for remote terminals, HP IB connection for external hard disk,and high-speed synchronous serial I/O for HDLC/SDLC/Bisync interfacing.

The system was called the F-85 and priced at about $5000 in the base configuration. Here's a photo of one:

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Here's the back of one; you can see all of the I/O connections:

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Eventually in 1979, Durango left the Apple neighborhood on Bubb Road and moved into snazzy new digs on north First Street in San Jose. Instead of almost having to sit in my office partner's lap, I now had a private office with a real door. The downside was that the new neighborhood was very industrial-commercial ("tilt-up" city) and it was hard to find a good falafel for lunch.

The first hard disk for the F-85 was a suitcase-sized affair using the Shugart SA-4006 14" winchester and a bipolar bit-slice controller (from Microsystems Consultants) and interfacing over the HP-IB link. Up to 40 MB could be accommodated.

A multipass high-resolution printer upgrade followed, complete with downloadable fonts and proportional spacing (the pictured system has one of these), followed by double-sided diskette drives for almost a megabyte on a diskette and then eventually a 5.25" Rodime hard disk taking the place of one of the floppies (an external floppy drive box was always an option). Bank-switched (in 1K chunks) add-on RAM was also an option. Durango dropped the "F-85" model name and adopted a system that used model numbers that corresponded to the various installed options; 700 being the entry model and 950 being the full-featured model. A 600 model was planned (complete with an orange case (This was the 70's, after all), but not marketed.

The Software

The F-85 featured a multitasking operating system called DX-85M, which included an integral Indexed Sequential (ISAM) file system and per-task file locking. The implementation language for applications was called Star BASIC and was a compiled-to-P-code system complete with the usual multi-tasking mechanisms (semaphores, inter-process communication). CP/M and MP/M from Digital Research was offered as an option.

Up to 5 users could be connected simultaneously to the F-85, using the serial ports in addition to the main console. Keyboards and character sets were supplied for major European languages, Thai and Katakana (marketing in Japan was handled by Mitsui Electrical Corp.).

An interesting coincidence was that I/O drivers could be selectively loaded at boot time using directives from a text file called--CONFIG.SYS (history is funny that way). All of the MCBA business applications were adapted and debugged for the F-85, as well as a word processing package and a spreadsheet developed by Chang Labs.

The price point of the F-85 with hard disk was in the neighborhood of $13,000. Too expensive to use as a personal computer, but very favorably priced against most of the available minicomputers. About 5000 F-85s were manufactured and sold.

The Decline and Fall

In mid-1981, IBM released for sale a much-rumored "personal" computer, named the 5150. When taken as just another entry in the market, it didn't seem like much. It was expensive and rather underpowered. What was under-appreciated was the public perception of IBM as "the" computer company and the wide acceptance of the PC.

Durango had been planning a 16-bit system for some time, based on the Intel 8086, but decided to go IBM one better and market a completely new system using the 80186 and the 80286 as an add-in option. The Durango "Poppy" was born. MS-DOS was selected as the entry operating system, the integrated printer was dropped (Japanese printers from Epson, Oki and NEC were priced below the cost of incorporating one). The integrated video and keyboard were abandoned in favor of a standard terminal made by Beehive.

With the 80286, one could run Xenix in multi-tasking mode, but the 80186-only version was stuck with MS-DOS and single user mode. A decision was made to use 'C' as the programming language and the re-launching of the MCBA applications and Star BASIC under Xenix resulted in an implemntation that ran no faster than the lowly F-85.

Worst of all, the MS-DOS implementation was PC-compatible only in a cosmetic way--all of the I/O was different; there was no compatible BIOS and no memory-mapped video.

Priced at significantly more than a PC, it was inevitable that sales would be lackluster at best. It was worse than that--sales plummeted.

In 1982, Durango merged with Molecular Systems in a mutual attempt to keep the wolf from the door. Molecular's specialty was a multi-user S-100 system using one processor per user. A great idea, but no competition for the ubiquitous PC. The new Molecular went into Chapter 7 bankruptcy in 1984.

It was a great ride while it lasted!

Here's a sales brochure circa 1980 for the F85

Here's a photo of the 14" hard disk controller.

Chuck Guzis, October, 2006

If you happen to own a Poppy and want to sell it or swap it for an F85 (I have two), drop me a line! I'd like to complete my rogues' gallery!

If you spy any errors, please feel free to drop me an email at chuck at