Interview with AMD's Fred Weber - The Future of AMD Microprocessors

Weber's Thoughts on Cell

Ever since its official introduction, we've been going around asking everyone we ran into about their thoughts on IBM/Sony/Toshiba's Cell microprocessor, and Fred Weber was no different.  Surprisingly enough, Weber's response to the Cell question was quite similar to Justin Rattner's take on Cell.  Weber saw two problems with Cell:

1. Cell is too far ahead of its time in terms of manufacturing, and
2. Cell is a bit too heterogeneous in its programming model, referring to Cell's approach as both asymmetric and heterogeneous (we'll explain this in a bit).

As we concluded in our Cell investigation, the approach to microprocessor design of having one general purpose core surrounded by several smaller cores is not one that is unique to Cell.  Intel has now publicly stated that this heterogeneous multi-core approach is, at a high level, something that they will be pursuing in the next decade.  The problem is that to be produced on a 90nm process, the individual cores that make up Cell has to be significantly reduced in complexity, which Weber saw as an unreasonable sacrifice at the current stage. 

The next problem that Weber touched on was the Cell approach to a heterogeneous multi-core microprocessor.  To Fred Weber, a heterogeneous multi-core microprocessor is one that has a collection of cores, each one of which can execute the same code, but some can do so better than others - the decision of which to use being determined by the compiler.  Weber referred to his version of heterogeneous multi-core as symmetric in this sense.  Cell does not have this symmetric luxury; instead, all of their cores are not equally capable and thus, in Weber's opinion, Cell requires that the software needs to know too much about its architecture to perform well.  The move to a more general purpose, symmetric yet heterogeneous array of cores would require that each core on Cell must get bigger and more complex, which directly relates back to Weber (and our) first problem with Cell that it is too far ahead of its time from a manufacturing standpoint.