How to Choose the 68 Pin SCSI Cable? The Definitive Resource for Purchasing a 68 Pin SCSI Cable.

Shenzhen, China (PRUnderground) July 23rd, 2026

The 68 Pin SCSI Cable is the highest point of development for the Wide SCSI timeline. The 68 Pin interface was introduced as part of the new SCSI-2/SCSI-3/Wide SCSI/Ultra320 specification standards and provided a method of doubling data width (from 8 bits to 16 bits), which in turn allowed for significant increases in throughput and allowed for SCSI to remain viable throughout the 1990s and into the 2000s.

Today, the 68-pin SCSI-3 cable plays a key role in a wide range of active systems, including enterprise RAID arrays, tape libraries, high-end document scanners, medical imaging systems, and industrial data acquisition systems. The challenge in selecting a proper cable lies not only in the wide variety of cable variants available but also in the multitude of signal standards and termination requirements.

A 68 Pin SCSI cable buying guide for IT administrators and system builders, Data Center Managers, and Industrial Maintenance Technicians who need to learn how to use the 16-bit Wide SCSI bus. I will show you how to identify connectors: HD68, VHDCI, HPDB68, and the differences between the connectors. You will be able to determine which SCSI cable is best for your application using the HD68, VHDCI, or HPDB68 connector type. In addition, I will discuss the three different types of shielding, the signaling you’ll need on your SCSI cable (single-ended (SE) or differential), or low-voltage differential (LVD), and best practices for terminating your Cable.

The company offers a range of connectivity solutions available in one place, where customers have access to our comprehensive range of connectivity solutions, including SCSI cable, which includes all the necessary cables required by your business, including VHDCI cable, MDR cable, SCSI-2 cable, Centronics SCSI cable, 50 Pin SCSI cable, IDC Cable, and D-sub cable.

The 68-Pin SCSI Connection Family: There are three SCSI connector types in the 68-pin ecosystem.

Basically, the term “68-Pin SCSI Cable” refers to three different mechanical connector types, although all carry the same electrical signals of Wide SCSI with 68 pins. Therefore, understanding the differences between connector families is essential when selecting the correct 68-Pin SCSI Cable for a RAID and Tape Drive application.

1. The HD68/HPDB68 Wide SCSI (External)

It is probably the most prevalent External Wide SCSI connector, introduced in SCSI-2 Wide up through Ultra320. Features:

• D-subminiature shell, about 47 mm by 11 mm.
• There are two rows of 34 terminals spaced at 0.050th inch (1.27 mm) apart, or at half pitch.
• Thumbscrews or latch locks with #4-40 threads are used for locking.
• The term “HPDB68 SCSI cable” or “Half-Pitch DB68” is also acceptable.
• These devices can be found on the external SCSI ports of the host adapters, in RAID enclosures, tape libraries, and high-end scanners.

2. VHDCI 68-Pin (Very High Density Cable Interconnect)

This connector was developed as a space-saving alternative to the previous connectors. The key features of a VHDCI connector are as follows:

• It has an extremely thin outer shell, about 33 mm wide and 9 mm high.
• The terminal block has two rows of 34 contacts spaced 0.800 mm apart.
• The device is equipped with thumbscrews (angled) to provide stability for stacking adjacent devices.
• It is nearly half as thick as an HD68.
• Available on: National Instruments DAQ cards; Multi-port SCSI HBAs, densely populated RAID controllers.

3. HPDB68 (Alternate form factor)

Many manufacturers define HPDB68 as having a slightly offset D-shaped shell. Although they may appear similar, the terms HD68 and HPDB68 should not be used interchangeably, and physical compatibility must always be confirmed with your equipment.

Guide to Quickly Identifying SCSI Connectors Visually

Width is a very obvious way to tell the difference between HD68, VHDCI, and HPDB68 68-pin SCSI connectors when you’re checking out the port on your equipment. The HD68 connector has basically the same width as the VGA port on your monitor; the VHDCI connector is quite a bit thinner than the HD68 and only slightly wider than a standard RJ45 Ethernet connector.

Electrical Properties: The Wide SCSI Advantage

The SCSI-2, SCSI-3, Wide SCSI, and Ultra320 SCSI standards (Small Computer System Interface) define the electrical characteristics associated with the 68 Pin SCSI Cable. The wide 16-bit data bus allows for twice the throughput as compared to what is available using the Narrow SCSI standard, but with backward compatibility to previous standards.

Bus Specifications:

• Data Width is 16 bits (wide bus) with parity.
• Signaling is single-ended (SE), differential, or Low Voltage Differential (LVD)—the standard for Ultra160 and Ultra320.
• Bus speed:
  • The maximum transfer rate of the Fast Wide SCSI bus is 20 MB/s.
  • The maximum transfer rate of the Wide SCSI bus is 40 MB/s.
  • The Ultra2 Wide LVD had a maximum transfer rate of 80 MB/s.
  • The Ultra160 had a maximum transfer rate of 160 MB/s.
  • Ultra320: 320 MB/s
• Device Count: Up to 15 devices (IDs 0-14) and a host adapter (ID 15)
• Termination: Both ends of the physical bus must be terminated.

Are Ultra160 and Ultra320 supported by a 68 Pin SCSI Cable?

When determining whether a 68-pin SCSI cable can support the Ultra160 and Ultra320 transfer rates, the answer depends on the type of cable used to connect the two devices. Ultra320, which operates at a transfer rate of 320 megabytes per second, requires a cable that meets all of the following cable specifications:

• Strict impedance control (132 ohms +/- 5 percent differential).
• Low amount of crosstalk between conductors.
• Low signal strength loss.
• LVD signal compatibility.

Reliable Ultra320 performance requires premium cable with 28 AWG and/or 30 AWG twisted pairs and overall braid shield, and rigorous quality control. Using low-quality cables can cause the bus to negotiate down to Ultra160 or slower.

Cable Construction: Designing to Ensure High-Speed Performance Standards

A 68 Pin SCSI Cable (aka Wide SCSI Cable) performs a critical function in the data transfer between devices connected via Wide SCSI interfaces and must be precisely engineered to enhance its high-speed capabilities. Wide SCSI Cables support Ultra160 and Ultra320 data transfer rates and, therefore, require a greater level of attention to detail regarding the cables’ electrical properties.

Shielding Design

There is no question that in an EMI-sensitive environment, such as a Data Center or Industrial application, the Shielded 68 Pin SCSI Cable will provide optimum performance over the unshielded version:

• Each Pair is Individually Wrapped in Aluminium Foil as Individual Pair Shielding.
• The Tinned Copper Braid has an Overall Shield of Tinned Copper Braid (≥85% Coverage) across the Entire Bundle.
• Ferrite Core: The ferrite beads & cores are located on one or both of the cable ends to suppress common-mode noise (EMI).
• 360° Ground: Shielded metallic connector back shell connected to metallic shield to form a Faraday cage.

Conductor Arrangements (Conductor Configuration)

• It can never be said enough that the importance of twisted pair and impedance control in 68-Pin SCSI Cable Conductor Configuration shall not be neglected. Signal integrity at Ultra 320 speeds and frequency (160MHz clock speed).
• Each differential signal pair is isolated, twisted pair, shielded by a braid, and has 132 ohms ± 5% impedance, conforming to the (LVD specification).
• Twisted-pair skew is minimized by maintaining equal pair lengths.
• Stranded conductors: allow more flexibility in rack-mounted installations.

Connector Quality

• HD68 SCSI cable (Full Metal Back Shell, Gold Plated, Minimum 30µ” Thickness, Robust Thumbscrews, Latch Lock.)
• HPDB68 SCSI cable: Ensure that the connectors fit into the port openings of all connected devices.
• Strain Relief: The Molded Long Boot at the Connector Entry protects the conductors from breaking.

The Types of Signaling: Single-Ended (SE), Low-Voltage Differential (LVD), and Their Use in Multimode Situations

Knowing the types of signals provided (Single-Ended [SE] / Differential / LVD [Low Voltage Differential]) is very important for locating and checking the pinouts on a 68-pin SCSI cable and on an L-type SCSI (LVD and SE).

Single-Ended (SE):

• Each signal is referenced to a common ground.
• Bus lengths are limited to 3 Meters for Ultra Wide and up to 6 Meters for Fast Wide.
• Single-ended signaling was used in earlier implementations of SCSI2/WIDE.
• Single-ended devices are compatible with LVD multimode devices but operate only in SE mode (i.e., LVD multimode devices will operate as SE when attached to SE devices).

LVD (Low Voltage Differential):

• With LVD signaling, each signal is transmitted as a differential pair (i.e., Positive / Negative).
• Maximum bus length of 12 meters, or 25 meters with a limited number of devices.
• Ultra2, Ultra160, and Ultra320 are standard.
• Lower power requirements and better protection against noise than SE.

Multimode (LVD/SE) devices

• Devices that automatically negotiate between LVD and SE.
• Fallback to SE if an SE-only device is attached to the bus.
• Cables must be able to handle the slower negotiated mode.

Important Warning!

High Voltage Differential (HVD) is a method used in earlier versions of SCSI and will not work with either SE or LVD devices. If you connect an HVD device to an SE/LVD bus (or vice versa), there is a good chance you will damage the transceiver chips. So, be sure you’re connecting the correct types of signals.

Termination: Essential for the Reliable Operation of Wide SCSI Systems

Incorrect termination remains the primary reason for SCSI bus failures at higher speeds. You must have a clear understanding of active versus passive termination to ensure high reliability of SCSI-3 68-pin cable systems.

Passive Termination:

• Simple resistor-based networks (e.g., 220/330 Ohms).
• Can only be used for Wide SCSI at speeds above 20 MB/s.
• Do NOT use passive termination for any Wide Ultra SCSI or LVD SCSI application.

Active Termination:

• The voltage regulator (LVD = 2.85 V), the precision resistor, and the device’s impedance are measured.
• Impedance is tightly matched over 68 signal cables.
• Required for use in Ultra160/Ultra320
• External dongle devices or built-in.

LVD-Specific Termination

• This requires the use of terminators rated for LVD signaling (132Ω differential).
• Active LVD terminators maintain proper signal quality at the highest speeds.
• Some include indicator LEDs to show bus status.

Termination Rules for 68-pin Wide SCSI are:

• There is a terminator at each physical end of the Bus.
• All intermediate (non-physical end) devices must have termination set to “off” or disabled.
• An External terminator plugs into the unused SCSI port on the last SCSI device (on an external SCSI cable).
• LVD termination is required for both Ultra160 and Ultra320 LVD SCSI devices.
• Mixing LVD devices with SE devices forces all LVD devices into SE operating mode, resulting in performance degradation.

68 Pin SCSI Cable Signal Attenuation

SCSI-3 16-bit length maximums are largely determined by the signaling type (Fast vs. Ultra) and the speed at which the cables run (from 12 MB / sec to 160 MB / sec).

If you run cables longer than the listed maximum length for a specific application, you will experience a gradual loss of signal integrity, an increasing amount of crosstalk, increasing signal attenuation and reflection, and the following problems:

• Bit error rates (BERs) are increasing.
• Repeated attempts to recover data at deteriorating speeds.
• Buses are locked out, or timeouts occur.
• The entire communication has stopped.

When possible, avoid exceeding 3 meters of cable in an Ultra320 installation. When connecting the Ultra320, you will want to use a high-quality cable with 28 AWG or 30 AWG twisted-pair configurations and a braided shield covering the entire length of the cable.

Practical Applications: RAID, Tape, and Beyond

The type of 68-pin SCSI Cable you’ll need for your Ultra320 or Wide SCSI system depends on how you plan to use it.

RAID Arrays:

• External RAID Enclosures: An HD68 SCSI cable generally connects your HBA to your RAID enclosure.
• Multi-Port Configurations: You can use a VHDCI cable when multiple connections are needed on a single slot bracket.
• Cable Length: Most people will use 0.5m to 3m cable lengths for rack installations, but you should always check the total bus length of your configuration (including all attached devices).

Tape Libraries:

• Enterprise tape drives (LTO, DLT, SDLT) generally use either the HD68 or VHDCI interface.
• Autoloaders: If you have more than one drive connected to your SCSI bus, be sure to accurately measure the total length of your SCSI connection.
• Cable Routing: When your cable is often moved around, choose a flexible cable with a strong thumbscrew or latch lock.

Document Scanners:

• Production Scanners: Fujitsu, Kodak, and Epson are all brands of high-performance production scanners. Most of these models come equipped with an HPDB68 SCSI connection.
• Connecting Older Scanners: Some older-model scanners require a special connector (called a custom “pinout”), so you will want to check the manufacturer’s specifications before connecting them.

Industrial Data Acquisition (DAQ):

• National Instruments: National Instruments’ many PXI & SCXI (modular DAQ) systems use high-density VHDCI connectors for acquiring data from multiple channels simultaneously.
• Testing Equipment: HD68 connections are used for attaching probes (oscilloscopes, logic analyzers, etc).

Pinout Verification: Make Sure You Got the Right Pinout Checked.

A standard SCSI-3 SPI pinout was used for the 68 SCSI cable and L-type LVD_SE cables. Here is how to verify that your SCSI Cable is wired correctly.

The following signals are assigned by the SCSI-3 SPI (SCSI Parallel Interface) standards.

• Differential Pairs: Data signals DB(0) to DB(15) as well as parity DBP.
• Control Signals: BSY, SEL, REQ, ACK, MSG, C/D, I/O, ATN.
• Ground Returns: intermixed between signal pairs.
• Termination Power: TERMPWR (pin number varies for connector type).

Most external 68-pin SCSI cables (male-to-male) for rack-mount applications with butterfly screws use a direct connection (from pin 1 to pin 1). An exception to this rule would be some crossover-wired, internal-to-external transition-type cables, and it is imperative to check the pin configuration with a continuity tester if it is not known.

Internal vs External: Substituting HD68 Ribbon for IDC Ribbon

The migration from internal IDC 68-pin ribbons to external HD68 cables is commonly requested. Internal SCSI cords are constructed of 68-wire flat ribbon with IDC-type connectors, whereas external SCSI hookups utilize a cable of the same length, but are sheathed in a shielding wrap and have an HD68-type tip connecting the cable to the device.

To convert an existing internal SCSI connection to an external connection, you need to do the following:

• You would also need to use a SCSI host adaptor that includes an external HD68 (mil-spec) connector or a mounting bracket with an external HD68 port.
• Use a 68-pin IDC-to-HD68 transition cable: one end has an IDC connector for the drive, and the other has a shielded HD68 connector for external routing.
• Check that the cable is compatible with the necessary signaling speed (Ultra160 or Ultra320)
• Implement proper termination on both sides of the bus.

BespokeCable creates custom 68-pin ribbon assemblies using precision Insulation Displacement Contacts to make the final termination for IDC Cable users.

Quality Indicators: What to Look For

When sourcing a 68 Pin SCSI Cable, inspect these quality markers:

HD68 SCSI cables/HPDB68 SCSI cables are both ultra160/ultra320-grade materials required for ensure the reliability of Ultra160/Ultra320 SCSI connectivity. The use of a marginal-quality cable may result in random errors that are extremely difficult to diagnose.

Installation Best Practices

Please adhere to the following steps for smooth installation and operation of your SCSI-3 68-pin cables:

• Turn Off All Devices Prior To Connecting Or Disconnecting. LVD SCSI can be hot-plugged with some controllers (but it is not recommended).
• Finger-tighten thumbscrews plus one-quarter turn. Over-tightening can strip out the threads.
• Allow a Bend Radius Equal To Four Times the Outer Diameter Of The Cable. For Shielded Cables, This Would Be Approximately 30 Millimeters.
• Keep the cable route away from sources of noise such as power cords, The Power Supply Units (PSUs) Of A Server, or any Motor Drive. At least Six Inches of Separation is recommended.
• Verify the proper termination. The termination on the bus should be activated only on the bus’s last device.
• Set unique SCSI IDs. Devices other than the host should have different IDs (0-14).
• Label the cables in multi-device chains with the length, destination, and installation date for each segment.
• Document the bus topology for future troubleshooting purposes. This includes the device IDs, the termination points, and the overall cable length.

Problems and Solutions

To troubleshoot your 68 Pin SCSI Cable issues, follow the steps below methodically:

Symptom: Device Not Found or Occasionally Found

• Check the screw type of all thumb screws (ensure they are tightened).
• Verify the termination on both ends of your SCSI light bus.
• Verify SCSI IDs are unique among devices.
• Test the cable with a known good device.
• Check if the connector has bent pins.
• If possible, try using a shorter cable.

Symptom: Lower-Than-Expected Speed Performance

• Confirm that all devices used in your testing support the selected speed for the SCSI Bus (i.e., Ultra160/Ultra320).
• Check if one of your devices is an SE-Only device and is forcing the bus into a slower mode.
• Confirm that the cable used is rated to provide the desired operating speed.
• Check if the LVD termination is installed correctly.
• Confirm if the bus’s total length complies with the manufacturer’s specification.

Symptom(s) of intermittent errors occur while the system is loaded

• Examine the cable to ensure it is not kinked, crushed, or otherwise physically damaged, and keep it close to the EMI source.
• Replace the cable with another model/type that has more shielding
• Reduce the number of devices attached to the bus.
• Consider isolating the device with intermittent errors from the rest of the devices on that bus.

Symptom(s) of bus hang(s), no communication happening between all devices, and/or timeouts

• Disconnect all devices and restart them.
• Disconnecting devices, one at a time, until the faulty device is found.
• Make sure the signaling type is appropriate for the connected devices (see SE, LVD, or HVD in this guide).
• Only have one device and one host on the SCSI cable when running tests.
• Replace the cable with a new, known good cable.

Conclusion: High-speed SCSI means Accurate Connections

Speedy performance is what precision connectors provide through the 68 Pin SCSI Cable, the top-performing cable of parallel SCSI. An understanding of the several types of connectors, the standards for signal transmission, and the quality standards will assist the end-user in choosing the appropriate cable(s) for Ultra160 or Ultra320 speeds. With this understanding, it becomes extremely easy to choose the right cable, regardless of whether you need an HD68 SCSI Cable for an Enterprise RAID Array, a VHDCI Cable for Dense Multi-Port HBA, or an HPDB68 SCSI Cable for Production Scanner.

If you practise the differences between HD68 Vs VHDCI vs HPDB68 68-pin SCSI Connectors, also proper use of Active or Passive Termination using LVD Compatible Terminators and the correct cable selection to meet the performance requirements set out herein with good 28 AWG / 30 AWG Twisted Pair/Overall Braid Shield and Ferrite Beads/Ferrite Cores (EMI Suppression), you will achieve the maximum throughput on your 16-bit Wide SCSI Bus without any errors.

BespokeCable offers custom-made cables of the highest quality that are constructed to meet the needs of the harshest enterprise and industrial environments and include cable types, such as SCSI-2 Cable, Centronics SCSI Cable, 50 Pin SCSI Cable, MDR Cable, IDC Cable for internal ribbon connections, or D-SUB Cable for serial or parallel legacy applications.

About Bespokecable (68 Pin SCSI Cable)

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