Now that 100-Mbps desktop Ethernet connections have become commonplace, network administrators are looking for the next silver bullet to improve network performance. Gigabit Ethernet, also known as 1000BaseT, running at ten times the speed of 100BaseT, promises to be that silver bullet. Alas, today’s Mac CPUs can’t achieve Gigabit’s full potential. Even on a Power Mac G3, the fastest speed attainable with Gigabit Ethernet is barely twice the speed of 100-Mbps Ethernet. Still, as CPUs gain speed, they’ll be able to take advantage of improved network performance. To that end, we checked out three Gigabit Ethernet PCI cards: Asanté Technologies’ AsantéFast 1000 GigaNIC, Farallon’s PN9000-SX, and Team ASA’s Stallion GE-II.
All three products are easy to install: just plug in the card, load the drivers, and reboot. Hooking up the cards’ fiber-optic connections is as simple as with copper Ethernet, but you can run the wires much farther: up to 500 meters.
The CPU speed limits Gigabit Ethernet performance because of the processing overhead. Standard Ethernet packets are a maximum of 1,500 bytes long, which means a computer must process more than 80,000 packets every second to achieve Gigabit Ethernet’s full throughput. It turns out that a Power Macintosh G3 can process only about a fifth of that, limiting performance to less than 100 Mbps. To circumvent this problem, Gigabit Ethernet supports larger packetscalled jumbo framesof up to 9,000 bytes each. With these larger frames, theoretically even a G3 Mac can move data at a gigabit per second. Unfortunately, the Mac OS doesn’t yet support jumbo frames, so this capability is largely unusable. Team ASA bundles a utility that lets you transfer files using jumbo frames, but you can’t mount volumes or copy files through the Finder, and the program won’t run under Mac OS 8.6.
All three products provide performance-boosting aids, including offloaded TCP/IP checksum generation and full-duplex communication. Asanté supports the Ethernet 802.3 p and 802.3 q quality-of-service standards, especially useful in multimedia networks. Team ASA’s card ships with Mac OS X drivers.
On-board diagnostic aids are a big help in troubleshooting network woes. Asanté’s GigaNIC excels here, with six status indicators for power, link, transmit, receive, bus type, and flow control.
Faster, but Not by Much
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