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Exclusive First Look: Adaptec 3950U2B
64-bit PCI Dual Channel Ultra2 SCSI controller for the B&W G3

Published: 4/17/99

card pix - click for larger  view

As reported at the main site news recently, Adaptec has been shipping the 3950U2B 64-Bit PCI dual-channel Ultra2 SCSI controller to Apple for several weeks. I suspect it will appear as an option at the Apple Store soon, and wanted to provide you with a sneak peek at what is without a doubt the most capable 'data pump' currently available for a personal computer.

The Adaptec 3950U2B provides high bandwidth, dual-channel Ultra2 SCSI coupled to a 64-Bit PCI interface, making it an ideal card for high-performance servers and workstations. The two independent Ultra2 SCSI channels combine to provide a maximum data transfer rate of 160 MBytes/sec, 4 times that of a std UltraWide SCSI PCI Card. I'd love to see the rates possible with this card driving a 4 drive (or more) 10,000 RPM U2 RAID 0 array.

Take one B&W G3 with adequate RAM (128MB-256MB or more), running OS X server and equipped with the 3950U2B driving a pair of Cheetahs or IBM LXZ drives you'd have one screaming web or file server I'm sure.

With dual Ultra2 interfaces and legacy SCSI support on one card, the 3950 is a great slot saver with plenty of performance headroom for the future. I've bought more SCSI cards/flavors than I can count over the years, but owners of the 3950 should be set for the forseeable future.

performance chart  of SCSI interfaces

The 3950U2's 64-bit PCI bus interface (266MB/sec max) prevents the possibility of the PCI bus bottlenecking the dual Ultra2 SCSI channels (up to 160MB/sec), as 32-Bit PCI maxes out at 132MB/sec . (Note: Most pre-G3 Macs can't achieve the PCI maximum 132MB/sec rate however, due to PCI/Memory controller and system bus limits). The 3950U2B also works in non-B&W G3 systems, as the card is designed to be compabile with both 32-Bit and 64-Bit PCI interfaces. For best performance a 64-Bit PCI slot should be used, especially with mult-drive arrays.

3950U2B Features:

  • Up to 160 MByte/sec data transfer rate on two Ultra2 SCSI channels in a single 64-Bit PCI slot

  • 64-Bit PCI interface ensures bus bandwith exceeds maximum SCSI I/O rate

  • Connections for up to 30 SCSI devices

  • Advanced multimode I/O cell that accommodates either Ultra2 or legacy single-ended SCSI devices

  • Each of the two channels support up to 15 devices on a 12 meter cable

There is only one downside to the Mac 3950U2B - as I mentioned in the news a few weeks back, there are no plans for a retail version. It will only be available from the Apple Store as a BTO option (or a service part perhaps?). Perhaps Apple might consider offering it to existing B&W G3 owners as they did with the internal modems.

Related Links:

For other Site B&W G3 Articles (HD upgrades, compatibility, speed settings and more) see the links on the main Yosemite page.


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