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ATTO ExpressPCI UL4S and ExpressPCI UL4D SCSI Adapters

Volume Number: 22 (2006)
Issue Number: 04
Column Tag: Review

ATTO ExpressPCI UL4S and ExpressPCI UL4D SCSI Adapters


by MacTech Staff

SCSI on Mac OS X

For those of you who have been around to remember SCSI on early Mac OS X, you'll likely recall that SCSI on Mac OS X 10.0 and 10.1, and even to some extent 10.2, was a nightmare: troublesome, error prone, and unreliable. Ultimately, Apple re-wrote the SCSI implementation, and SCSI on Panther and beyond has worked as it should. It would be a mistake to judge SCSI today by those early experiences.

Today's SCSI Experience

When it comes to SCSI on the Mac, the first name that comes to mind is ATTO. ATTO has a variety of technologies, SCSI and others, and a variety of form factors. In our case, we looked at the single connector ExpressPCI UL4S, and the dual connector ExpressPCI UL4D SCSI adapters.

Simply put, these products provided a very pleasurable experience -- we installed the cards, and they worked. No drivers. No hassles. It just worked, and it worked well.

To be fair, many people may prefer FibreChannel. It all comes down to what you want to connect to, what is available to you, and what you want the future path to be. If you do choose FibreChannel, you should also take a look at what ATTO has to offer as they are strong there as well.

The Details of SCSI

ATTO ExpressPCI UL4S and ExpressPCI UL4D SCSI adapters are part of the Ultra320 SCSI host adapter series for data intensive enterprise servers and high-end workstations running applications such as high-end video editing, database engines, messaging, and web servers. UL4S and UL4D support up to 30 SCSI bus IDs and Low Voltage Differential (LVD) for cabling up to 12.5 meters per bus. Both products are compatible with single-ended SCSI devices, providing cable distances up to 3 meters. UL4S is a single channel Ultra320SCSI, PCI-X host adapter with data transfer rate of 320 MB/sec, whereas UL4D is a dual channel Ultra320SCSI, PCI-X host adapter with data transfer rate of up to 640 MB/sec. UL4S and UL4D are compatible with Mac OS X, Windows Server 2003, Windows XP, Windows 2000, and Linux. Dynamic bus rescan is available for Mac OS X only.

While 3 meters of cable is recommended for most applications, when we did our install, the drive was in the rack, and the PowerMac wasn't. We reached out to see what cables were available in longer lengths. We found the folks at 9 To 5 Computer Supply <> had a 10m (yes, 30 feet) cable, and they sent it over for us to take a look at. 9to5 also has a range of other "toys", new and refurbished, with a focus on mass storage solutions.

We plugged the long cable in, and the throughput was spectacular between the ATTO card and the Quantum SDLT II. Be careful when you order cables as there's a variety of connectors for the SCSI 3. In our case, we needed a VHDCI male to HD68.

UL4D is equipped with two external VHDCI, and two internal high-density 68-pin connectors. It is 6.521 inches in length and 4.450 inches in height. UL4S features one external high-density 68-pin connector, and one internal high-density 68-pin connector. It is 6.521 inches in length and 4.2 inches in height. UL4D is Mac G5 compatible, and it is available as a standalone or part of an ExpressRAID Kit that includes ExpressRAID Software.

ExpressPCI UL4D

ExpressPCI UL4S

The UL4S and UL4D both feature a 64-bit/133 MHz PCI-X bus with compatibility to PCI-X 1.0a and PCI 2.2. Accelerated PCI bus management enables PCI Bus Master rate of 1-GB/sec. UL4S and UL4D can operate in temperature range of 0-45 degrees C, humidity 10-90% non-condensing, and airflow 100 LFM (min). Power rating of both SCSI adapters is 0.75 typical/2.0 max. Amps @ + 5.0 /VDC, and 0.05 Amps @ + 12.0 VDC with PCI signal compatibility of 3.3 Volts/5 Volts. In terms of reliability of these products, MTBF (mean time between failures) is 150,000 hours, and MTTR (mean time to repair) is less than 15 minutes.

Backward Compatibility and Advanced Streaming

While we were focused on SCSI-3 and newer technologies, there are times you want to be able to use older items. ATTO's proprietary Vpath Technology enables the UL4S, and UL4D to offer users the flexibility of connecting high-speed Ultra320 devices externally, and slower legacy devices internally, or vice versa, without compromising on the performance of the high-speed device. Backward compatibility is supported for Ultra 160, Ultra2, Ultra/WIDE, Fast/WIDE and Narrow SCSI devices. The UL4S and UL4D are ASPI (Windows) compatible, RAID ready, PC 99 compliant, plug and play compatible, feature Flash ROM for easy field upgrades, and supports automatic and upper-byte termination for narrow devices.

The Advance Data Streaming (ADS) feature provides controlled acceleration of data transfers utilizing optimized SCSI-3 algorithms, embedded RISC I/O processors for low overhead, and optimized gather/scatter of lists. ADS, facilitates bus mastering eliminating CPU processing time as bottleneck. Tagged command queuing in ADS allows efficient processing of threads, and disconnect/reconnect reduces wait time between transfers.

The UL4S and UL4D also support Ultra320 specific features such as packetized SCSI, read/write data streaming, training patterns, pre-compensation, double transition clocking, Quick Arbitration Select (QAS), Cyclical Redundancy Checking (CRC), Domain Validation (DV), Asynchronous Information Protection (AIP), free-running clock, and flow control. They also support multiple block sizes, and are bootable from attached disks.

UL4S and UL4D come with ATTO ExpressPro-Tools and ATTO Configuration Tool formatting, and utility software. UL4S and UL4D are priced at $349 and $499 respectively. Both products are RoHS compliant (2002/95/EC).

Avalable at

MacTech Staff


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