At the Microprocessor Forum in October, five companies unveiled new DSP architectures. This was also the debut for one of these companies, Siroyan, a UK startup backed by venture capital. Siroyan had previously been a quiet presence in the DSP world, but now it has taken a very aggressive stance on scalability—its new architecture targets applications that range from ultra cost-sensitive disk drives to high performance wireless communications infrastructure.
The Siroyan OneDSP architecture, which employs a VLIW approach, is based on the concept of "clusters." A cluster is essentially a complete processor outfitted with its own execution units and a variety of dedicated resources, e.g., registers and local memory. Each cluster in the OneDSP handles two VLIW slots: one for loads/stores and one for computation. Despite the self-sufficiency of the clusters, the OneDSP uses a single control thread. Thus, at least from a programmer's perspective, the OneDSP resembles a traditional VLIW machine.
The advantage of the cluster approach is scalability. In the high-performance 'C6xxx family from Texas Instruments, for example, each register file has read and write ports for each of four execution units. Given this already complex register circuitry, adding more execution units would be a serious challenge. In contrast, adding execution units to the OneDSP would have little impact on the existing circuits because clusters are connected in a nearest-neighbor topography. This building-block approach to scalability is similar to that found in the BOPS ManArray architecture, which has many other features in common with the OneDSP. Scalability is increasingly important as today's DSP applications become more and more demanding on processors.
The OneDSP is entering an already crowded field of VLIW architectures, but Siroyan may be able to capitalize on the mistakes made by its predecessors. Siroyan's extreme approach to wide ranging scalability—if it works—should go a long way towards earning the company a foothold in the market for licensable DSP architectures.
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