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Our PowerDomain 2940U2W review is our lastest report
on SCSI technology. In our original RAID review, I
looked at how an Ultra Wide SCSI card and corresponding hard drives can boost the
performance of practically any Mac system. The RAID review looks at how regular end
users can utilize these technologies, especially as prices continue to fall.
In Part One of our Ultra2 SCSI review, I look at
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| SCSI Term |
Bus Width |
Burst Speed |
| SCSI (I) |
8 bit |
5 MB/sec |
| Fast SCSI (II) |
8 bit |
10 MB/sec |
| Fast Wide SCSI |
16 bit |
20 MB/sec |
| Ultra SCSI |
8 bit |
20 MB/sec |
| Wide Ultra SCSI (III) |
16 bit |
40 MB/sec |
| Ultra2 SCSI (LVD) |
8 bit |
40 MB/sec |
| Wide Ultra2 SCSI (LVD) |
16 bit |
80 MB/sec |
| Wide Ultra3 SCSI (LVD) |
16 bit |
160 MB/sec |
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Data Source: Quantum Corp.
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Ultra2 SCSI technology without any specific hardware in mind. Part One is the first
in a series of reviews and serves as a primer for Ultra2 SCSI. This review serves
as Part Two of the Ultra2 SCSI series
While working with Ultra2 SCSI over the past three months, one thing I must point
out is that Ultra2 may not be quite as simple as Mac users may be accustomed to using.
SCSI never really has been an exact science, and I found the higher the performance,
the more sensitive the technology. This is not to say Ultra2 does not work or that
it is difficult to set up, but rather I am trying to convey that we’re not exactly
talking about Zip drives. Ultra2 introduces a new tier in disk performance and functionality.
With that performance, there will obviously be higher costs and may require additional
tweaking.
Hardware: AHA-2940U2W
Adaptec’s offering is uniquely configured and has some built-in advantages. The main
differentiation is the card utilizes SpeedFlex
technology. SpeedFlex offers a solution for using different types of SCSI drives
on the same card without losing Ultra2 functionality.  The card has a total of four SCSI ports. There’s
an external 68-pin Ultra2 SCSI port, which can use all flavors of SCSI. On the internal
part of the card, there is another 68-pin Ultra2 port, a 68-pin Ultra Wide port,
and a 50-pin Ultra Narrow port. In summary, this card can handle all flavors of SCSI.
Currently all Ultra2 cards on the market can do this, with at worst an adapter. However
typically if Ultra and Ultra2 drives share the same bus, the entire bus will run
in Ultra mode. With SpeedFlex, the Adaptec card can run Ultra2 and Ultra drives at
the same time while keeping the Ultra2 drives in Ultra2 mode. It is important to
note however that LVD drives can only utilize Ultra2 features/speeds when they are
hooked up to one of the two Ultra2 ports. This means if you want to use Ultra2 and
Ultra drives on the same card, the Ultra drives must use one of the two internal
Ultra ports.
While I’ve experienced criticism of Adaptec’s SpeedFlex implementation, I personally
like the idea. When testing I found only an insignificant drop is performance while
using Ultra2 and Ultra drives on the same card. Other SCSI card vendors are suggesting
a more robust approach to the problem by using dual channel Ultra2 cards. Both options
allow Macs users to have both Ultra2 and Ultra SCSI devices on a Mac without taking
up two PCI slots.
Software
The 2940U2W comes with an Ultra2 version of Adaptec’s PowerDomain control application.
I found the application to be fairly intuitive and to the point. It only needs to
run when the user wishes to modify the card, so it can stay out of the way. There
really isn’t much to say about it — it does the job.
Benchmarks
I’ve provided benchmarks comparing the 2940U2W card to the Initio Miles Ultra Wide
card. All tests were done on Seagate Cheetah Ultra2 Wide/LVD hard drives.  Because of
compatibility problems, all tests were performed using a 180 MHz 604e PPC in an 8500
with 160 MB of RAM, 256K cache, and 96K disk cache. Conley's SoftRAID was used to
format and configure the disks. Disk tests are presented using the Remus benchmarking
package and MacBench 4.0. Each card was tested in a single fixed disk configuration
and a two disk array.
To summarize the data, I found Adaptec’s 2940U2W card to give consistent performance
benefits from Ultra SCSI. Of particular interest, benchmarks showed only a slight
variation in performance when both Ultra2 and Ultra drives were used simultaneously
on the card. I decided to test the SpeedFlex features by booting off of an Ultra
drive, and testing the Ultra2 drives on the same card.
Compared to other Ultra2 SCSI cards, I’m also reviewing ATTO’s ExpressPCI Ultra2
card. For benchmarks, preliminary testing shows both cards are fairly comparable.
Incompatibilities
As with the 2940UW, the 2940U2W is incompatible with PowerLogix and PowerLogix-based
G3 upgrade cards. While I didn’t find any definitive problems with the Adaptec card
and my G3 upgrade, both Adaptec and PowerLogix confirm the problem. In my correspondences
with the two companies, it doesn’t look like the problem is going away any time soon.
The 2940U2W however works with PowerPC 604e processors, Newer Technology G3 upgrades,
and Apple’s PowerMac G3s. Other G3 upgrade cards may be compatible, however Newer
Technology is the only vendor that is currently known to be compatible.
Termination Problems
When I first looked at the Adaptec card, I was originally sent two Quantum drives
and an Adaptec 2940U2W card. Both pieces of hardware were pre-production units. The
card and drives operated correctly, however seemed slow. In fact, my Ultra Wide SCSI
card at times beat out the Ultra2 card and drives.
 For this
review, Adaptec sent me two Cheetah drives on loan from Seagate, which were shipping
models, and a shipping firmware upgrade for the 2940U2W card. Adaptec also sent me
an external cable and an external Ultra2 diagnostic terminator. This time, performance
was more than what I expected. However I found an odd problem with the card and its
onboard termination. After considerable testing, it appeared the card had problems
terminated the second Ultra2 connector when running in Ultra2 mode. The card worked
fine for Ultra mode, however when an Ultra2 drive was connected to only one of the
two Ultra2 ports, the drives would not appear on the bus.
This left me scratching my head and Adaptec said this should obviously not be happening.
To solve the problem, I resorted to doing something a little unorthodox. I placed
an Ultra2-LVD external terminator on the external port of the Adaptec card while
placing Ultra2 drives on the internal connector. It worked, and the diagnostic terminator
was reporting Ultra2 mode.
I’m not too sure what to make of this situation. It is possible I did not have the
cabling hooked up correctly, however when testing an ATTO Ultra2 card with the same
drives/cable/terminator configuration, everything appeared to work correctly. Adaptec
said they have never seen this happen before with their cards, so I’m willing to
entertain the possibility that it has something to do with my specific set-up.
As of publication, this issue is left unresolved. Adaptec has sent a new card to
me, however I'm awaiting a new pair of Ultra2 drives for testing. Look for an update
to this situation in the future.
Conclusions
The 2940U2W can support a wide range of SCSI configurations -- something other single
channel cards can not do. Adaptec has a long history of SCSI technology, and offers
a compelling product for Mac users. I personally experienced problems with the model
that is currently shipping, however I’ve found no indication what could be the cause
of the problem. From start to end, I’ve worked with this card for over three months.
I used it as my primary SCSI host for that time, and I did not experience any other
problems. Once the card was functioning correctly, it worked great.
Pros — SpeedFlex offers an excellent path for a legacy convergence to Ultra2
technology. Users won’t have to take the big plunge into Ultra2 all at one time.
Our preliminary testing shows it is very comparable to ATTO’s Ultra2 SCSI card.
Cons — Incompatible with PowerLogix based G3 upgrades, still an expensive
upgrade, however Ultra2 prices are falling. I personally found problems with the
card’s two LVD connectors and termination.
• I wanted to give special thanks to Adaptec and Seagate for providing hardware and
support for this review.
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