Opteron Vs. Athlon X2

[Bill Broadley]

On Mon, Dec 05, 2005 at 10:42:14PM -0500, Bryan J. Smith wrote:
> On Mon, 2005-12-05 at 19:35 -0500, Peter Arremann wrote:
>> E6 stepping has better memory timing capability (400 with a higher number of 
>> memory banks)
> 
> Huh?  All Socket-939/940 processors have 4x 32-bit banks (2x 64-bit DDR
> channels).  FYI, Socket-754 + 184 (2nd DDR channel traces) = 938.  ;->

On the older revision chips the memory bus would be down clocked if
you had a larger number of banks, I don't remember the numbers
exactly but something like 4 banks = PC2700 and 8 banks = PC2100.

The E4/E6 maintain PC3200 for a larger number of banks.

> > On the other side, if you go for dual 2xx opterons and you pay extra for a 
> > good board, you get a huge improvement on IO. Multiple PCI-X busses and the 
> > like are nice to have on most servers but for a developers workstation it 
> > doesn't really matter.
> 
> As long as you don't need more than 100MBps in disk and network.
> Otherwise, PCI-X is still much better because most desktop mainboards
> only ship with PCIe x1 channels outside of video.

Many of the s939 boards have single or dual GigE on the motherboard, even
the midrange boards have pci-e 2x (like the MSI K8N neo4) AND dual GigE.
All the SLI boards (even the cheapie foxconn for $120) supports a x8
slot for fancy RAID or networking if you need it.  Getting a second 16x
slot is possible but does add a significant premium (around $100). 

So I find it hard to believe where any workstation would need PCI-X
unless there's some strange pci-x only card required.  8 SATA ports
are also relatively easy to come by on the motherboard.  

What I would consider is that for CPU intensive use whether you need
a second memory bus or not, if your running 2 cache-unfriendly jobs a
second socket (assuming a 4+4 memory system) can double the throughput
when compared to a single socket system.  Alas, it also incurs a
substantial cost, size, and heat penalty.

Personally I'd get a single socket, pci-e, and a dual core if the
price point made sense and I planned to be running > 1 CPU intensive
job.  Of course there are many workloads that would justify different
configurations.

-- 
Bill Broadley
Computational Science and Engineering
UC Davis