Specifications

Starting With StarFabric:The StarFabric Connectivity Guide 11
Six Reasons to Migrate to StarFabric
• Latency: Devices in PCI and CompactPCI chassis can’t communicate simulta-
neously because of the shared bus. So devices have to take turns passing data.
The higher priority traffic takes precedence over everyday traffic. Competition
on the bus means delays and latency for real-time applications.
Since StarFabric connections are point-to-point, devices communicate simulta-
neously. There is little latency during device communications. Devices can com-
municate concurrently or simultaneously with no waiting. In sophisticated
StarFabric applications, data prioritization can be configured so you control
how long it tales for traffic to be transmitted across the StarFabric.
• Performance Limitations: PCI’s bandwidth doesn’t meet all the demands of
large enterprise server networks when it comes to speed and scalability. Today’s
fastest PCI bus is a 64-bit bus operating at 66 MHz to transfer data at a rate of
about 533 MB/s or about 4.1 Gbps, but it’s still a shared bus capable of support-
ing only a few slots. In fact, slot count becomes a big issue with PCI’s higher
speeds. Basically, faster clock speeds mean fewer slots. PCI.X promises
1.0 GB/s bandwidth at 133 MHz clock speed, but it supports only one expansion
slot at that speed, making it a speciality card implementation at best. If you want
more slots, PCI.X must operate at lower speeds (100 MHz for two slots and 66
MHz for four slots), basically bringing true bandwidth down to around
500 MB/s or about 4.1 Gbps for all practical purposes.
Performance is not an issue with StarFabric technology. Bandwidth scales from
2.5 Gbps per link (that’s 622 Mbps per serial connection) to 5.0 Gbps when the
links are aggregated in bridge and gateway applications, and up to 30 Gbps for
StarFabric switching applications. Furthermore, bandwidth has no limitation
on the number of expansions slots you can add in your topology. Every connec-
tion is point-to-point, so you can add as many expansion chassis as you need
without impacting the overall bandwidth.
• Distance Limitations: Existing PCI standards limit you to short distances of
one meter (three feet) between I/O expansion devices, often requiring expen-
sive, proprietary cables. The electrical characteristics of PCI transmission often
mean lower speeds for data traffic.
Each StarFabric connection is a direct point-to-point link using Low Voltage
Digital Signalling (LVDS) over standard RJ-45 cables. This means greater dis-
tances and higher speeds for expansion chassis, so room -scale configurations
up to five meters (fifteen feet) are not a problem. LVDS provides electrical char-
acteristics that support higher frequencies for longer distance, so StarFabric
achieves bandwidth speeds up to 2.5 Gbps each or 5.0 Gbps aggregated for fast