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(ALTODOCS)TFS.TTY;9 FRI 28-0CT-77 11:35AM PAGE 1

For Xerox Internal Use Only -- October 28, 1977

Trident disk software October 21, 1977 1

Software and Utilities for Trident Disks:
Tfs, Tfu, Triex

1. Introduction

This document describes Bcpl-based software for operating any of the
family of Trident disk drives attached to an Alto using a "Trident
controller card" (the software presently deals with the T-80 and T-300
models). Hardware and diagnostic information can be found in the
document "Trident disk for the Alto" (on (ALTODOCS)TRIDENT.EARS). by
Roger Bates.
The software documentation is divided into three parts: (1) a brief
"how-to" section describing the software package available for
operating the Trident; (2) a section describing two useful utility
programs. Tfu and Triex; and (3) a section describing the software
package in more detail. There is a short revision history at the end.
The Tfs package and utilities all assume that the disk is to be
formatted with 9 sectors per track, 1024 data words per sector. Thus a
T-80 disk has a capacity (815 tracks, 5 surfaces, 9 sectors, 1024 words
per sector) of 36,675 pages or 37,555,200 words. A T-300 (19 surfaces
rather than 5) has a capacity of 139,365 pages or 142,709,760 words;
however, due to the restriction of virtual disk addresses to 16 bits, a
single file system may utilize only about 47 percent of this capacity,
and it is necessary to construct multiple file systems in order to make
use of the entire disk.
Because of bandwidth limitations, it is unwise to operate the Trident
disk while the Alto display is on. Although the Tfs package will save
the display state, turn it off, run the disk, and restore the display
for every transfer, the user may prefer to turn the display off
himself. The Tfs management of the display causes the screen to flash
objectionably whenever frequent calls to Tfs are underway.

2. Trident File System (Tfs) software package

The software for operating the Trident disk is contained in
(Alto)Tfs.Dm, and consists of the following relocatable files:
Tfslnit.Br, TfsBase.Br, TfsA.Br, TfsWrite.Br TfsCreate.Br, TfsClose.Br,
TfsDDMgr.Br, TfsNewDisk.Br, TfsSwat.Br. and TriConMc.Br. The
definitions file Tfs.D is also included. The LoadRam.Br file, formerly
included as part of the Tfs, is now available as a separate package.
(ALTODOCS)TFS.TTY;9 FRI 28-0CT-77 11:35AM PAGE 1