[Beowulf] dual-core benefits?

[Tahir Malas]

Hi everyone,

I would like to take advice for the processor selection for the cluster that
we will configure soon. Comparing the sequential performance of our programs
on an Opteron 246 and a much more expensive machine with Itanium Processor,
we have decided to use opteron processors with Tyan mbs. However, we are in
a confusion to decide on the processor selection. Before posing my
questions, I'd better give some info about our application requirements:

1. The scalability of our program is not so good, less then 20 for 32 nodes
(measured on a single node system). So we don't plan to go beyond 16 nodes.
(which makes 32 processors due to dual-node usage)

2. Memory requirement is huge; we will use 4GB memory per node for the time
being and increase this to 16 GB later. So wee need fast CPUs and efficient
usage of memory.

3. Due to budget limitations we will first configure 8-node system with 4GB
RAM per node and extend this to a 16-node system with 16-GB of RAM in 6
months.

We were thinking of AMD 250 processors, but now the benchmarks of dual-core
CPUs (on the web site of AMD) seems encouraging, and the cost of dual-core
AMD 275 seems to be less then twice of AMD 250. Since the memory cost of our
system will dominate other costs, we can afford to pass to dual-core
technology. However, the questions that arise are follows.

1. Will it worth? And can we gain any advantages over single-core with the
not-so-good scalability of our parallel programs? 

2. Another question is that is dual-core technology brings any advantages
for the efficient usage of high amount of memory that we will utilize? 3. 3.


3. Finally there is something basic that I'm not sure: When we assign a job
to dual-core CPU, can it divide it between the core-CPUs automatically, or
should we think dual-core CPU the same as dual-node CPU? If the latter is
the case, what is the advantage of this technology over dual-node?

If anyone has info and/or experiences about these, I will be very glad to
know. 

Thanks in advance,
Tahir Malas
Bilkent University 
Electrical and Electronics Engineering Department
Phone: +90 312 290 1385