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We tested the SunATM 622 adapter in a pair of Sun Ultra-2 computers with two processors and 256 MB of RAM. The adapter installation was straightforward, and we had no problems connecting to our FORE Systems ASX-200BX switch. We measured performance and recorded the Unix load aver age of the machine during our tests. Keep in mind that an idle system has a load average around 0.01, and a server may fluctuate between 1.0 and 4.0 or more while servicing normal enterprise activities. In our benchmarks, the 622 adapter could pump out about 225 Mbps with a load average of 11. Sun suggested that performance could be improved to about 350 Mbps in a n ATM-only environment by increasing the maximum transfer unit (MTU) to 9,253 bytes from 1,500 bytes.

As a comparison to our PCI 155 adapters, we also tested two SunATM 155 adapters in the Ultra-2 server. At its best, the Ultra-2 was able to handle 256 Mbps of full-duplex traffic--more than 100 Mbps faster than any of the PCI ATM adapters we tested. Although comparing PCI and SBUS adapters is like comparing apples to oranges, it is obvious that the Solaris platform has made leaps and bounds in performance and demonstrates a higher degree of scalability than an equivalent two-processor, two-PCI bus Intel machine. ATM technology benefits from Solar is and the SBUS architecture and offers tangible increases in performance that may very well cost-justify using ATM. The SBUS 155 adapters are comparably priced at $995 and $1,295 for fiber and unshielded twisted pair (UTP) versions, respectively. The fiber SBUS 622 adapter lists at $4,995.