Single Core2Duo Quadcore vs. two dualcore Xeon?

[Martin Cracauer]

Johan Strm wrote on Thu, Aug 02, 2007 at 10:41:13PM +0200: 
> Hello
> 
> I'm in the process of purchasing a new server. I'm currently looking  
> at two Supermicro based options, one with a Core 2 Duo Q6600 Quadcore  
> 2.4GHz 2x4MB (on a PDSMi+ board) , and another with two Xeon 5110  
> dualcore 1.6GHz 4MB (on a X7DVL-i board).

Well,  the 2.4 GHz will be faster than the 1.6 Ghz :-)

I'll assume for the rest of this mail you compare equal speed
processors. 

> Both configurations would have 4GB (2x2Gb) memory (to begin with, 4  
> slots on the boards so max 8GB), and I'm thinking about 4x 500GB  
> disks in a raid10 config on a 3Ware 9550SX.
> 
> What my question is, from the performance point of view, what would  
> be best? Two dualcores or a single quadcore? 

There's two dies inside these Quad chips anyway, and everything goes
through the same northbridge and memory controller even in the 2-CPU
soltuion.  The performance difference is almost NIL given same
clockspeed and same memory speed.

> I'm thinking about  
> memory bandwidth and such... 

The FB-DIMMs are bashed by some for high latency and maybe that's true
if you use all slots.  Personally I couldn't observe this, 667 MHz
FB-DIMMs perform about as 667 MHz unregistered for me.

However, the 775 platform allows you to either buy 800 MHz memory, or
even overclock memory, so potentially you get much more memory
bandwidth if you require it.

On the other hand, the better 5xxx Xeons had 1333 MHz FSB for longer
and I think the Q6600 is still 1066.  Doesn't do much in real-world
performance either, though.

> Bus bandwitdh (to ethernet and disks)...

That depends on the busses on the board.  Typically you'll get PCI-X
on socket 771 boards but very rarely socket 775 boards have any.

> Looking from the upgrade point of view I guess two dualcores can be  
> replaced with two quadcores, but on the other hand, if that will be  
> necessary  then another box is probably a better solution...

The dual 771 platform also allow much more memory.  I find 8 GB to be
very tight these days.

> Is there any known problems with FreeBSD and these stuff? From what  
> I've understood Supermicro is pretty FreeBSD-friendly and should work  
> fine...

Supermicro has nothing to do with any of this, it's all integrated
into the chipset and some single chips on the board.  But yes, the
Intel chipsets are as FreeBSD-friendly as it gets.

Martin
-- 
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
Martin Cracauer <cracauer at cons.org>   http://www.cons.org/cracauer/
FreeBSD - where you want to go, today.      http://www.freebsd.org/