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by Peter Dzwig
So Intel have canned Larrabee and gone to 48-core clouds on chips. Is it really that simple?
The short answer is “yes” and “no”.
Intel have been looking at a variety of architectures over a period of time. This is an obvious step: if they are going to change their core counts beyond the (relatively) few cores that they have on production chips at present then they need to understand what the issues are going to be and what design strategies are useful. The Terascale chip (aka Polaris) was a very different beast from the recently announced 48-core processor, being 80 VLIW-core based so looking nothing like an x86 configuration and described by some who knew as barely programmable. Nonetheless there were apparently a lot of lessons. Intel describe the latter as “primarily a circuit experiment” and SCC as “a circuit and software research vehicle”.
The current processor is (apparently) readily programmable, being “IA-compatible” and so can run off-the-shelf apps. It's uses message-passing shared virtual memory and actors. It is also made on 45 nm technology. However if the announcement is to be taken at face-value then this too will not make it to production.
Its not that surprising that Intel appears to be slowing down work on Larrabee, given its on/off history and changes of configuration, rumoured or otherwise. It is very unlikey though that Intel would want to loose the experience and technological benefit gained from developing it. That's not how engineering progresses. My guess is that some of the developments will re-appear in some shape or form in future products.
These are all steps along the road.
If I were being asked what will make it to production my guess is that it will be not look a great deal like any of these. A heterogeneous hybrid with several different types of cores, some targeted at specific problems might be closer. Whatever does appear will contain lessons that have come from all of these processors, and from all Intel's other multicore processors – and Pentiums too. Probably the 48-core system is somewhat closer to what is likely to be reality than Terascale ever really was. Given the predicted growth in numbers of cores on a chip then for reasons of engineering and programmability it would appear that distributed memory and some kind of network is the way to go. IA will most probably be implemented in some shape or form, if only for backwards compatibility.
It is also interesting to speculate how Intel will address its future markets. Traditionally the embedded market has seen different architectures. However the commercial challenge of widely differing novel architectures will be great. Whether or not this leads to some design rationalisation is still to be seen. Would multiple, possibly divergent, processor lines make commercial sense in the nearer term?