two 100 tpi high-capacity 5.25-inch diskette drives storing 480 KB on each single-sided or 960 KB on double-sided diskettes using group-coded recording (GCR)
The Durango F-85 was an early personal computer introduced in September 1978 by Durango Systems Corporation, a company started in 1977 by George E. Comstock, John M. Scandalios and Charles L. Waggoner, all formerly of Diablo Systems.[1][2][3] The F-85 could run its own multitasking operating system called DX-85M, which included an integral Indexed Sequential (ISAM) file system and per-task file locking, or alternatively CP/M-80.[1][4][5] DX-85M utilized a text configuration file named CONFIG.SYS[5] five years before this filename was used for a similar purpose under MS-DOS/PC DOS 2.0 in 1983.
^The product flyer for the Durango 800 series documents a formatted "on-line capacity" of 1.892 MB for the diskette drives. The system, however, was equipped with two 5¼-inch Micropolis100 tpi 77-track floppy drives by default, and 1.892 MB is about twice as large as the physical drive capacity documented in various other sources (480 KB per side), therefore, by "on-line capacity" they must have meant the available storage capacity available to users for the combination of two drives.
^ abcdComstock, George E. (2003-08-13). "Oral History of George Comstock"(PDF). Interviewed by Hendrie, Gardner. Mountain View, California, USA: Computer History Museum. CHM X2727.2004. Archived(PDF) from the original on 2017-03-23. Retrieved 2017-03-23. […] that's how we got Durango Systems started in 1977. And we opened the doors for business I think it was July or August of '77 and began designing a product, one of which is sitting right there. That's the Durango F85 computer […] We were on the startup of Durango, we raised our money and got going and in that case it took us another 15 months to start shipping product […]
^ abGuzis, Charles P. (2009-09-13). "Durango GCR". Sydex. Archived from the original on 2017-03-25. Retrieved 2017-03-25.
^"NCC Preview: OEMs at NCC - Micropolis Corp". Computerworld. XII (22). CW Communications, Inc.: P/50. 1978-05-28. Retrieved 2017-06-12. […] Micropolis has extended the capacity of 5.25-in. floppy disk subsystems via double-sided models with formatted file storage of up to nearly 2 million bytes […] The Megafloppy series also features an intelligent controller that facilitates interconnection of four subsystems to a common host interface for a total on-line storage capacity of more than 15M bytes […] Double-sided versions of the product line will be implemented first in two OEM series - Model 1015 and Model 1055 […] The Model 1015 is an unpackaged drive designed for the manufacturer who integrates floppy disk storage into his own system enclosure. A range of storage capacities from 143,000 to 630,000 bytes per drive is available […] Model 1015 customers have the option of using the Micropolis intelligent controller and Group Code Recording (GCR) method to further expand file space up to 946,000 bytes […] Offering GCR and a microprocessor-based controller as standard features, the Model 1055 5.25-in. floppy has four soft-sectored formats for each of its 77 tracks, yielding a maximum capacity of 1,892,000 bytes of file space on its double-sided version […] An add-on module available for the 1055 is comprised of two read/write heads and two drives, sharing a common controller. The subsystem capacity (formatted) with the module is 3,784,000 bytes […] Up to four 1055s, each with an add-on module, can be daisy-chained to a common host for a maximum on-line storage capacity of more than 15M bytes […]