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REVIEW: Atto's UL5D PCI Express Ultra320 SCSI Host Adapter

Posted February 17th, 2006, by rob-ART morgan, mad scientist

With all the attention to Serial ATA, we haven't done much with SCSI host adapters or drives lately. But when Atto Technology announced the PCI Express UL5D host adapter for the Dual-Core and Quad-Core G5 Power Mac, we were anxious to test it.

We were hoping to test the UL5D with the Seagate 146GB Cheetah 15K.4 (ST3146854LW) drive because it received a high 93MB/s low level transfer speed rating from Storage Review -- but we weren't able to shake any eval units loose from Seagate. They did, however, provide us with two 73GB Cheetah 15K.3 drives (ST373453LW) -- 76MB/s low level rating.

In the graphs below, we compare the Cheetahs in single and striped pairs to the reputed fastest Serial ATA drives -- the Western Digital Raptors. We tested a single WD Raptor 10K Serial ATA 150GB (WD1500ADFD, 16MB cache) drive -- 88MB/s low level rating. Plus we tested a single and striped pair of 74GB WD Raptor 10K Serial ATA drives (WD740GD, 8MB cache) -- 72MB/s low level rating.

The Serial ATA host adapter we used was the new Sonnet Tempo SATA E4P (SATA-300) PCI Express host adapter. (The Tempo SATA E4P and E4i have been announced and will soon begin shipping. Test system was a Quad-Core G5/2.5GHz Power Mac with 4GB of memory.)

(Our random graphs below reflect the average of 256K, 512K, and 1024K block transfers.)

At least among the drives we tested, the 10K SATA drive were just as fast as or faster than the 15K SCSI drives in sustained and random transfers.

Ultra320 SCSI storage does have distinct advantages. You can hang multiple drives on each Ultra SCSI channel, achieving the full 320MB/s per data channel. Though the Sonnet Tempo E4P SATA-300 host adapter supports multiple drives on each port, the best real world speed we've seen is 230MB/s per data channel.

The ATTO Technology UL5D PCI Express Ultra320 SCSI seemed to work fine except we were unable to test the drive using Zonebench or Disktester. For some reason those applications would freeze up without completing their run. We're checking with the usual suspects to see why that might be happening.

There's a cost/performance issue when comparing Ultra SCSI to "ultra" SATA:

Ultra320 SCSI
Host Adapter
Fastest 15K 150GB drive
Fastest 10K 150GB drive
Fastest 7K 300GB drive

(all drive price quotes are from

Other than cost, SATA has the advantage of supporting hot-swap in most cases.

Does it make economic sense to invest in Ultra320 SCSI PCI Express compatible on your Dual/Quad-Core system? Only if you already have a large investment in SCSI drives.

And if you are using 15K SCSI drives comparable to the ones we used, they aren't going to be any faster than the 10K SATA drives. In fact, in sustained transfers, they won't be any faster than the impressive 7K Maxtor MaXLine III SATA-300 (7V300F0) drive.

FLASH! On April 19th, 2006, Seagate announced a new Cheetah 15,000 RPM drive that's rated at 125MB/s -- the first single drive to break the 100MB/s barrier. The newest incarnation of the Cheetah, designated "15K.5," is available with 3Gb/s SAS (Serial Attached SCSI), Ultra320 SCSI and 4 Gb/s Fibre Channel interfaces. This flagship enterprise drive features 10 times the error protection and data reliability of the previous model. And it's the first 15K drive to use perpendicular technology, doubling capacity to 300GB.

QuickBench is included in SpeedTools Utilities, a product of Intech Software. They also have ZoneBench which allows you to sample the speed of a various zones in whole volume without filling it with real data.


Storage Review compares the 146GB Cheetah 15K.4 SCSI drive to others.

Storage Review compares the 150GB Raptor 10K SATA drive to others.

Storage Review compares the 73GB Cheetah 15K.3 SCSI drive to others.

Storage Review compares the 74GB Raptor 10K SATA drive to others


You can purchase the ExpressPCI UL5D direct from ATTO Technology's online store.

You can save $120 if you order from Small Dog Electronics. Though it's not list on Other World Computing, they are an ATTO dealer.


Granite Digital (cables, repeaters, terminators, and enclosures)

MacGurus (adapters, enclosures, and cables.)

Other World Computing (cables, adapters)

Small Dog Electronics (adapters, enclosures, and drives)


FirmTek (host adapters, enclosures)

Granite Digital (adapters, enclosures, drives, cables)

MacGurus (adapters, enclosures, drives, cables)

MaxUpgrades (adapters, enclosures, internal mounting kits)

Other World Computing (adapters, enclosures, drives)

Small Dog Electronics (adapters, enclosures, drives)

Sonnet Online Store (SATA II PCI Express and PCI-X host adapters) (enclosures, drives, internal mounting kits) (adapters, enclosures, pre-installed drives, internal mounting kits)

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2006 Rob Art Morgan
"BARE facts on Macintosh speed FEATS"
Email , the webmaster and mad scientist