High-endcomputer system architecture design can be divided into macro design and microdesign. Macro design is a kind of design for the whole large-scale computernetwork architecture, and micro design is for the single system/subsystem internalbackplate architecture. For the whole large-scale computer system design,distributed hierarchical network structure have been greatly used in the industrial,telecommunications, or defense systems, and this structure will not be greatly changedin the short term; but for the micro system (single system/Subsystem)architecture design, leaping improvement has been made along with the constant development of the processing capacity ofprocessor and data transmission technology.

2 Semiconductortechnology promotes the innovation of system micro architecture

The micro architecture of traditional computersystems usually adopts parallel structure based on VME, CPCI, VXI and otherstandards. However, with the rapid development of semiconductor technology inrecent years, various new structures have emerged such as SOC, which greatly increasesthe computing capacity of the single system (single node up to 574Gflops), andFabric (backplate switching) technology, which is based on HSSP (high speedserial differential Protocol) and solvesthe problems of high-speed, bulk data transmission through the backplate (microbackplate throughput can be increased to a magnitude of 100GBPS).

3 New switchingfabric for backplate - VPX

There are many kinds of popular switchingfabrics in the current market, especially the VPX, which is generally used forapplications with more stringent requirements of environment, size, powerconsumption and weight, such as military, aerospace, automotive, high-end industrialdata processing platforms etc.

VPX is a kind of bus standard ratherthan a parallel bus standard. VPX subvert the original concept of the parallelbus, it is a kind of point-to-point style backplate switching fabric, whichcustomizes micro-system point to point data switching topology through multiplebackplate HSSP signals. HSSP signals that support this switching architecturedesign include sRIO (serial Rapid IO), PCI-eXpress, 10GigaNet, 40GigaNet etc.

With the constant updating of 2-core, 4-core,8-core, 100-core and many core processors, the data switching capacity of the microsystem can reach hundreds of Gbps. Obviously, due to the limitations of busclock, data-bit width and electromagnetic interference, the traditionalparallel backplate system architecture has been no longer to meet so much datatraffic requirements.

However, high-speed data transmissionand anti-jamming capacity of VPX serial low-voltage differential signal haswell solved this problem, its latest high-speed differential signal rate is upto 10Gbps without the clock, data/address bit width constraints, meanwhile,this kind of high-speed differential signal can be used to bind ports accordingto the requirements of system design so as to realize multi-ports paralleltransmission and maximize data traffic. 300GB/s of data traffic can easily makeinteraction through the VPX backplate, which makes the throughput of the backplateincreased by over 100 times than that of traditional parallel bus architecture.

4 VPX backplate switchingarchitecture model

4.1 structure of star, mesh micro-systembackplate topology

Typically speaking, there are two kindsof VPX system switching architecture, namely the star and the mesh. The stararchitecture can extend the number of system load, generally up to 18 loads; itis generally divided into two types: single-star structure and binarystructure. The types of structure can be selected according to the complexityof the system. Figure 2 shows a single-star structure, from which we can seethat all the load nodes achieve point to point interconnection via the same fabricboard.

During the early stage of system design,we may often see that the mesh structure is used to build lab platforms or small-sizedexperimental system. This can achieve point to point high-speed serialinterconnection structure as well as saving the development costs during theearly stage. However, the number of backplate load have certain restriction, generallyless than five loads, then the whole mesh structure can be achieved. Figure 3shows the mesh structure with 5 loads.

Figure (3), mesh topology

4.2 hierarchical design of micro-structure

In the latest VPX standard, the designof micro backplate architecture fully utilizes the advantages of hierarchicalconcept that used in macro-system architecture design and divides the backplateswitching (Fabric) signal into five layers planes involving function plane,management plane, control plane, data plane and extended plane (Figure 4),thusrealizing a clear traffic control towards micro backplate data switching.

Figure (4), hierarchical model of micro-system backplatearchitecture

5 Typical systemarchitecture design

Figure 5 shows a kind of typicalhigh-end computer system design architecture, which is the case of AESA radarapplications. Macroscopically speaking, it adopts 3-layer network systemstructure; microscopically speaking, each system inside adopts backplateswitching structure. Each micro-system adopts five high-end single board digitalsignal processing computers (DSP), which interconnect with each other throughhigh speed HSSP port. This system design concept-from macro to micro, frommixing to stratification-will be the basis for future large-scale systemdesign.

Figure (5) Structure of a typical high-end computersystem design

Figure 6 is about the refinement of VPXmicro-architecture of the system, which uses five DSP computers, multiple DSP boards achieve high-speed backplate data switching via sRIO and the floating-point processing capacity of thesystem can be up to 384Gflops.

Figure (6), AESA case

6 Prediction of systemarchitecture development

Coming soon

Everything is changing all the time,including the system architecture design.. System design must fully take thecomplexity of the future system expansion and its compatibility into consideration.As the processing capacity of single micro-subsystem is constantly increasing, themacro system of multiple subsystems combined into a micro subsystem is alreadytechnically feasible. In the foreseeable future, with the technology, processdevelopment and the deepening of the importance of environment, the systemdesign at the macro structure will remain hierarchical structure and simplifiedas much as possible; and for the micro architecture, the system will bedesigned to achieve high performance, small size, low weight and low powerconsumption, or called SWaP.

References:

1, VITA46 Standard

2, OpenVPX Standard 1.2

3, Embedded Product Manual