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Introduction
Bridge Overview
Configuration Switches


INTRODUCTION

This document provides technical information for the Tableau T35i combination Forensic SATA/IDE Bridge.

The T35i combines two separate forensic bridges (IDE, and SATA) into one convenient package while providing native support for each hard disk technology. The T35i is designed to be installed permanently in the front of a forensic workstation or tower which has an open 5.25" half-height drive bay.

The T35i connects to the host computer through a FireWire800 (1394B) interface. Using FireWire as the interface to the host computer allows modern operating systems to recognize that the drives themselves are hot-swappable. This, in turn, eliminates the need to turn the host computer ON and OFF each time a new hard disk is attached or removed; only the T35i needs to be power cycled.

The combination of hot-swapping and the READ-ONLY forensic mode of operation make the T35i ideally suited for use in high-volume forensic applications.


BRIDGE OVERVIEW

The picture below is a close-up front view of the T35i.

The Table below describes each of the elements visible on the front of the T35i.

Front Element Description
Power Switch/LED The Power switch controls power to the T35i as well as to the DC OUT connector used for powering the connected hard disk.

The Power LED will be illuminated when there is power to the T35i and the power switch is in the "ON" position.
SATA Det LED The SATA Det LED (SATA Detect) illuminates when a hard disk attached to the SATA interface connector has been properly recognized. Only one hard disk may be connected to the T35i at a time.
IDE Det LED The IDE Det LED (IDE Detect) illuminates when a hard disk attached to the IDE interface connector has been properly recognized. Only one hard disk may be connected to the T35i at a time.
Host Det LED The Host Det LED (Host Detect) indicates when the connected hard disk has been recognized by the host computer. The Host Detect LED will illuminate only after the T35i has successfully identified a hard disk connected to the front of the T35i and after the host computer has "logged in" to the coresponding T35i channel using the FireWire/1394 SBP-2 protocol.
Wrt Blk LED The Wrt Blk LED (Write Block) is illuminated whenever the Tableau bridge is in READ-ONLY mode. This LED provides a positive indication that the bridge may be used to capture a forensically sound image from a subject hard disk.
Activity LED The Activity LED indicates that the host is performing some kind of I/O to the connected hard disk.
DC OUT Connector The DC Out connector may be used to provide power from the Tableau bridge to the subject hard disk. The DC Out output is controlled by the power switch. So, using the DC Out connector guarantees that the drive will be powered ON/OFF simultaneously with the T35i bridge.
Disk interface Connectors (SATA and IDE) The disk interface connectors attach the subject hard disk to the T35i. Tableau recommends the following cables:

Interface Cable
SATA TC3-8
IDE TC6-8 or TC6-2


The next image is a rear view of the T35i. Captions identify each internal T35i connector and the location of the configuration switches.


The following table describes each of the elements shown in the above picture.

Internal Element Description
1394B (FireWire 800) The T35i must be connected to the host computer via a FireWire800/1394B connection. This is the interface through which each of the T35i's two I/O channels will communicate with the host computer. It is acceptable to use FireWire400/1394A instead (with an appropriate cable adapter), but performance will be reduced.
DIP Switch Bank The T35i has one DIP switch bank with four switches. The next section in this document, Configuration Switches, describes the function of these switches in detail.
Power Power should be provided to the T35i through the standard 4-pin "Molex"-style power connector shown in the picture. The T35i requires approximately 450mA @ +5VDC for its internal operation. This figure does not include the power requirements of the hard disk connected to the DC OUT connector on the T35i.

IMPORTANT: Tableau strongly recommends that the T35i be on a dedicated power supply lead. Switching the T35i on/off can lead to large current/voltage surges which can interrupt the operation of other devices which share a power supply connection with the T35i.


CONFIGURATION SWITCHES

The following table summarizes the function of the four position DIP switch.

Operation
Switch Switch OFF Switch ON
1 Bridge operates in forced READ-ONLY mode and may be used to capture forensically sound images from subject hard disks. Bridge operates in READ-WRITE mode.
2 Bridge reports errors if host computer attempts to write when bridge is in READ-ONLY mode. Bridge does not report write errors when in READ-ONLY mode. (The bridge discards write data without returning an error.)
3 Bridge reports that it is WRITE-PROTECTED to the host computer when in READ-ONLY mode. Bridge does not report that it is WRITE-PROTECTED when in READ-ONLY mode.
4 This switch is RESERVED as must remain in the OFF position for correct operation.

The following table summarizes the recommended Tableau bridge configuration depending on the operating system you are using. These recommendations apply only when using the Tableau bridge in READ-ONLY mode to capture forensic images from subject hard drives (i.e., when the Write Block LED is illuminated).

O/S SW2-2 SW2-3 Comments
Windows XP OFF OFF In most situations, Windows XP handles READ-ONLY bridges correctly and will work optimally when leaving switches 2 and 3 in the OFF (default) state.

However, Tableau has seen cases where Windows XP will not allow a user to access a READ-ONLY partition. If you encounter a situation in which Windows XP reports that a volume is "write protected" and will not allow you to access the partition, then try the switch setting recommended for Windows 2000, below.
Windows 2000 ON ON Windows 2000 does not mount NTFS volumes correctly when the bridge declares that it is READ-ONLY. These settings make Windows 2000 believe the bridge is in READ-WRITE mode (even though it is not), and Windows 2000 will successfully mount NTFS volumes.
Windows ME/98se ON OFF Windows ME/98se may not recognize that a bridge is READ-ONLY and may attempt to write to the bridge anyway. If this happens, Windows ME/98se will generate a "blue screen" error. The recommended settings to the left eliminate the "blue screen" error.

NOTE: Some forensic users prefer to see the Windows "blue screen" error if a write is attempted. Users with this preferences should use the recommended settings for Windows XP instead.
Other OFF OFF Most other modern operating systems handle READ-ONLY forensic bridges correctly, so the default OFF settings are best for users of these operating systems.

IMPORTANT: As long as the Write Block LED is illuminated, the Tableau bridge will never permit writes or other modifications to the subject hard disk. Switches 2 and 3 only affect the way the bridge appears to behave from the perspective of the host computer.

NOTE: Switches 2 and 3 are ignored when the Tableau bridge is in READ-WRITE mode (i.e., when the Write Block LED is off).

 
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