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SKYchannel Interconnect: Increasing System Bandwidth

At the heart of the SKYbolt and Thunderbolt systems is the 64-bit ANSI/VITA standard SKYchannel Packet Bus. SKYchannel is the on-board communication path connecting the VME64 interface, the SKYrider parallel I/O, the System Processor, the compute modules, and high speed communication between Thunderbolt boards. The 320 MB/sec bandwidth coupled with SKY's crossbar architecture provides for multiple, simultaneous operations increasing available system bandwidth. SKYchannel provides reduced connection latency, split transaction, full-speed transfers, and forward progress mentioned above, the SKYchannel architecture brings several critical benefits to the application developer.

Large Flat Memory Space

SKYchannel provides for a memory-mapped 16 Terabtye address space. This enables application processors to perform simple loads and stores to access remote resources. Each VME board is allocated a 64 GB address space, which is more than sufficient to address all memory on a common VME memory board.

Built-in Error Detection

Transmission of data on a VME board and even between boards on a backplane is not error prone with current technology. However, for mission-critical applications where the highest data integrity is required, SKYchannel provides built-in error detection where there is the highest probability of an error, namely in the network connections between boards. This error detection is handled transparently by the hardware, as described below, by appending a checkword to each packet as it transits the backplane.

Heterogeneous Processing

The decoupling FIFOs and the modular interface of SKYchannel enables various types of processors to be interconnected. The speed of the processor's external memory bus does not need to be matched directly to the speed of SKYchannel.

320 MB/sec for each path

Having a fast, wide connection for each communication path is much better than trying to combine multiple slower connections to achieve the same aggregate performance. This is because each processor can use only one connection at a time and a fast processor will back up on a slower connection. Multiple SKYbolt or Thunderbolt boards can be connected for a total of up to 1600 MB/sec of bandwidth.