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					INTRO.TXT
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This file presents general information about the Symbios SDMS software
product. It is divided into the following sections:

General Description

Overview
	SCSI BIOS
	SCSI Device Drivers

Before You Begin
	Basic Rules For SCSI Host Bus Adapter and Device Installation

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*************************** General Description **************************

The Symbios SCSI Device Management System (SDMS) is a complete software 
package that solves the increasingly complex problem of managing system I/O. 
It seamlessly addresses hardware and software interfaces by supporting the 
Symbios family of SCSI processors and controllers, and a wide range of 
SCSI peripheral devices, while offering interoperability across application 
programs, operating systems, and host platforms. SDMS consists of a resident 
SCSI BIOS that manages all SCSI controller or processor specific functions, 
and a series of SCSI device drivers that provide operating system and 
peripheral specific support.

SDMS provides a standard method to interface SCSI I/O subsystems with devices, 
operating systems, and application software. It also enhances system 
capabilities already provided by SCSI controllers and processors by 
facilitating multi-threaded I/O support, system-wide SCSI device access, and 
creation of new applications.


******************************** Overview ********************************

An Symbios SCSI controller or processor can control peripherals such as 
hard disk drives, CD-ROM drives, tape drives, and removable media. SCSI 
peripherals are intelligent devices that do not need the constant attention 
required by non-intelligent devices. Up to 15 SCSI peripheral devices can be 
connected (via the SCSI bus) to a SCSI host bus adapter card on which the SCSI 
controller or processor resides.

A SCSI host bus adapter can also function as a secondary adapter in a system 
which already has a primary hard drive controller card (IDE, ESDI, ST506). 
Only SCSI host bus adapters will do this, expanding the possibilities for 
system configuration.

* SCSI BIOS *

A SCSI BIOS is the bootable ROM code that manages SCSI hardware resources. It 
is specific to a family of Symbios SCSI controllers or processors. An 
Symbios SCSI BIOS integrates with a standard system BIOS, extending the 
standard disk service routine provided through INT13. It is also responsible 
for processing and executing SCSI requests communicated from a SCSI device 
driver or application.

An important feature of the SCSI BIOS is that it is completely operating 
system independent. All ROM based SCSI BIOS support booting from a SCSI hard 
disk and can be ported to a variety of hardware platforms. They also support 
16- and 32-bit operating systems running under real or protected addressing 
modes.

The Symbios SCSI BIOS provides a hardware independent interface which 
isolates the operating system drivers and SCSI application programs from the 
underlying hardware. This enables a single driver to work with any host 
adapter or SCSI controller which has an Symbios SCSI BIOS.

During its boot time initialization, the SCSI BIOS determines if another hard 
disk is already installed. If there is, the SCSI BIOS will map any SCSI drives 
it finds behind the drive already installed. Otherwise, the SCSI BIOS will 
install drives starting with the system boot drive. In this case, the system 
will boot from a drive controlled by the SCSI BIOS.

If the operating system used is DOS 5.0 or above, the SCSI BIOS allows access 
to a maximum of eight SCSI hard disks via INT13. The number controlled by the 
SCSI BIOS depends on the number of non-SDMS controlled disk drives in the 
system. For more information on SCSI BIOS control of hard disk drives, see 
Chapter 2, Device Drivers for DOS/Windows. 

* SCSI Device Drivers *

The SCSI device drivers translate an operating system I/O request into a data 
structure, and transport the structure to the SCSI BIOS (see figure 1-2). An 
Symbios SCSI device driver is operating system specific, but completely 
hardware independent. The hardware specifics are addressed by the SCSI BIOS.

Although a driverless solution exists for the DOS operating system, and 
provides adequate support for many applications, loading a driver (or drivers 
in some cases) will provide additional features. Connecting peripherals other 
than hard disk drives, for example, requires loading the appropriate 
driver(s). 

The following chapters provide information on the use and installation of these 
drivers within each operating system.


**************************** Before You Begin ****************************

SDMS software requires an IBM PC/AT or compatible computer with an 80386 or 
higher microprocessor. An understanding of basic operating system commands is 
assumed. In addition, users of this manual should have a general knowledge of 
the SCSI standard. For background information on this subject, refer to the 
SCSI-2 specification or the book SCSI: Understanding the Small Computer 
System Interface. Sources for these publications are listed in the preface of 
this document.

Before using the SDMS software, the Symbios SCSI controller should be 
configured into your system, taking into account the configuration of other 
host bus adapters and system resources (see Basic Rules... listed below).

Symbios recommends that all data be backed up before making any changes 
or installing any software, including Symbios SCSI controllers and 
software. Failure to adhere to this accepted computer practice may lead to 
loss of data.

* Basic Rules For SCSI Host Bus Adapter and Device Installation *

Both ends of the SCSI bus must be terminated. Refer to the hardware manuals 
for the devices and the host bus adapter to determine what the terminators 
are, and where they are located.

Each SCSI device must be configured with a different ID number. Refer to the 
hardware manuals for the devices and the host bus adapter to locate where the 
jumpers or dip switches are for setting ID numbers. Usually the host bus 
adapter is ID 7. The devices are then set at IDs 0 through 6 (plus 8 through 
15 for wide SCSI). The bootable hard drive must have the lowest numerical ID. 

The red or blue line on a standard SCSI cable (or the black line on one end 
of a multi-colored SCSI cable) designates pin one on the cable connector and 
must connect to pin one on the device or host bus adapter connector. Refer to 
the hardware manuals for the devices and the controller to locate pin one of 
the connector.

If the system already has an internal bootable hard drive (IDE, ESDI, ST506), 
the drivers for the SCSI device(s) must reside on the internal bootable hard 
drive.

For non-PCI devices, whenever installing multiple host bus adapters in one 
system, each card must be set to a different base BIOS address, as long as 
the primary adapter has a lower base BIOS address than the secondary 
adapter(s). Also, make certain each adapter is set to a different base I/O 
address and IRQ.

