the ever-adaptable SCSI - Product Announcement

Emedia Professional, May, 2000 by David Doering

Adaptec Raises the Bar for Network Performance with Ultra160

adaptec's recent release of its new line of Ultra160 SCSI cards is noteworthy, for a variety of reasons. First, it marks the latest round in the escalating performance of PCs in general. At 160MB/sec--that's 160 megabytes--Ultra160 is the fastest way to connect peripherals to hosts. (200MB/sec Fibre Channel is just arriving as of this writing.) Second, Adaptec has gone aggressive with its pricing--actually introducing the line at a price point lower than its previous Ultra2 cards. Third, several of the cards provide simultaneous support for both LVD Ultra160 drives and Ultra2, and earlier SE SCSI drives. Finally, it definitely answers the critics' claim that Ultra2 SCSI was the swan song of the connector.

Clearly, Adaptec has learned from past SCSI marketing problems, and is making the connector much more appealing to this Internet-crazed, new-millennium crowd.

In the Beginning

SCSI's beginnings were pretty humble for those who remember. It is hard to imagine that SCSI has come all the way from 1981, when, at the dawn of PC pre-history, the Shugart Associates Systems Interface (SASI) debuted with--what was it--750KB/sec throughput? In June 1986, this interface became Small Computer Systems Interface (SCSI)--SCSI-1, if you are keeping count). SCSI-1 gave us a screaming 5MB/sec throughput.

We flip ahead to 2000, and we now have a bus capable of 32 times that original throughput--not bad for a 14-year-old technology. More importantly, the bus has become far more intelligent in this iteration.

This couldn't come at a better time for SCSI. With Western Digital quitting the SCSI drive business, there are fewer vendors still producing SCSI hard drives--Quantum, IBM, and Seagate being the only ones touting Ultra 160 drives. For those with an optical bent, there are also only a few vendors with DVD or CD readers/writers using the SCSI adapter. They include NEC, AOpen, Plextor, and Pioneer.

And even Plextor, long the home of SCSI-only aficianados, has now turned to offering an ATAPI device.

Adaptec is quick to point out that it isn't a failure of the SCSI technology that made it less popular; it was more a set of business decisions in releasing the previous upgrade. During the introduction of Ultra2 SCSI, the industry did not respond in a coordinated effort. Rather than deliver all the components needed for implementing a full Ultra2 SCSI solution, pieces were released over time.

As a result, for example, there was a lack of both terminators and drives, even though host adapters were readily available. Further, backward-compatibility was downplayed or poorly explained, leaving many users believing they could attach older Ultra SCSI drives to the longer Ultra2 SCSI cables and have them work (which they wouldn't).

This faulty introduction soured many people to SCSI, diverting their attention to the lower-performing but better-understood ATAPI bus. At least there, the system had backward-compatibility and preserved the current hardware investment.

It is clear that this time around, Adaptec would have none of that with the introduction of Ultra160, which not only comes complete and ready to go, but has legacy drive support on most of the cards.

What Puts the Ultra in Ultra160?

The Ultra 160 SCSI specification outlines five core and optional features that differentiate it from past SCSI versions. These include:

* Cyclical redundancy checking (CRC), which protects your data from being lost in the event of a poor connection or during a hot-swap of a new drive into the system

* Domain validation, which overcomes a problem with mixing legacy SCSI drives with Ultra 160 drives on the same bus. Domain validation checks to see if the bus and drive handle Ultra160 and if so, proceeds at that data transfer rate. If this rate isn't possible, domain validation allows the device to slip to a lower data transfer speed before data transfer begins

* Double-edge clocking, which allows for doubling performance in future versions of the bus, such as Ultra320 and Ultra640

* Packetization, which enables the adapter to send multiple commands, messages, status reports, and other data between SCSI devices in two data phases and at the fastest negotiated data rate. (This is an optional feature of Ultra160 SCSI devices)

* Quick arbitrate and select (QAS), which provides faster arbitration to reduce connect/disconnect time on the SCSI bus. This means that a QAS-supported device can give the bus to a second QAS-supported device that is waiting for bus time. It does this without the delay of having to enter a new arbitration phase. (This is another optional feature for Ultra160)

The challenge here is to differentiate between the Ultra3 specification of the SCSI Trade Association and Adaptec's (and others') version of Ultra3, that is the Ultra160 product time.

The Lineup

Adaptec is reducing the number of its SCSI host adapters down to four with the release of the Ultra160 products. These include two 32-bit PCI cards, the 19160 and 29160N; and two 64-bit cards, the 29160 and 39160.