Keith Bierman's Weblog

Tuesday December 06, 2005

Which Evolves Faster: Hardware or Software? Conventional wisdom has always had it that hardware is the "long pole"
in system design. Software can be changed up until the last moment (and
even beyond via patches). So the conventional answer is, of course, that
software evolves faster.

But, for large complex software is it really true? Let's consider the
new UltraSPARC T chips (formerly known as Niagara). As can be found
#link to hw_blog (anyone know the best pointer?) there are 32 hardware
threads per chip.

Given that these hardware threads are quite fundamentally different than
having 32 separate cores, just how does an OS such as Solaris deal with
them? The answer is by ignoring the differences and to a first
approximation treating them as 32 "CPUs".

This mostly works well; but it's interesting performance corner cases
that cause great confusion ... because the tools (e.g. mpstat) haven't
really evolved to keep up with the hardware for more details.

Sometimes the hardware does evolve faster.

Of course, the point of software layers such as an Operating System is to provide abstraction of hardware details. Just which hardware details need to be directly exposed is a deliberate process.

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