GSV said:
Start at the last page and work back!!
0c summary - dual core Opterons (and Xeons) are overpriced - two single
core CPUs of that class work out nearly as good as one dual core, for
less $ (and leave you an upgrade path).
Forgetting about Xeons and talking about Opterons only ...
If power consumption is important to you, then you need to factor
in that each of the single-core chips uses about the same amount
of power as a dual-core one at the same clock speed.
For workstations, if not servers, noise also becomes an issue.
For example, the Zalman CNPS7000 is a fairly quiet fan/sink, but
a system with two of them is still noticeably noisier than a
system with just one of them. You definitely don't want a box
with two of the AMD stock coolers on your desk.
At the 2 GHz level it costs about $400 (USD) more to go with one
Opty 270 instead of two Opty 246's. Performance is essentially
identical so you just have to decide whether it is worth $400 to
you to have an empty CPU socket available for an easy upgrade and
the reduced power consumption and noise.
That $400 price differential also stays more or less also applies
at the 2.2 GHz level (Opty 248 vs Opty 275) and 2.4 GHz level
(Opty 250 vs Opty 280), but it becomes lower in proportion to the
overall cost of the processors.
If you are sure that 2 cores is enough for you, then you can
go with Socket 939 for the 1P system - in which case a single
dual-core Athlon64 or Opteron with 1MB L2/core costs about $100
more than a pair of single core Opty 2xx at the same clock speed.
Factor in the motherboard savings and you can save an additional
$150 to $400 by going with a Socket 939 motherboard instead of a
2P motherboard. And with most of the 2P motherboards you will
have to get a more expensive E-ATX or rackmount case and will
need a more expensive EPS12V PSU instead of an ATX PSU.
However, if you want more than 4 GB RAM or if you need the PCI-X
slots that all but the cheapest 2P motherboard have, then a 1P
motherboard is not an option for you.