Dual Core or Quad Core?

[Warren Luebkeman]

On Friday 29 June 2007 11:58 am, Christopher Chisholm wrote:
> Derek Atkins wrote:
> > "Tom Buskey" <tom at buskey.name> writes:
> >> A few points:
> >>
> >> The Macintosh community had debates in the past about SMP vs single.
> >> Generally they think a dual 500 MHz is roughly like a single 700MHz. 
> >> From that subjective information, I'd say more cores that are slightly
> >> slower are better.
> >
> > This is probably true, as each core can be working on a separate
> > process so you have less context switching.
> >
> >> I've felt that dual CPUs have lower latency when multitasking.  The OS
> >> runs on one CPU, software raid (why spend more for a dedicated hardware
> >> raid card?), your App on another, etc.  IMHO latency is more important
> >> then throughput for interactive use.
> >
> > This is probably related to fewer context switches, but keep in mind
> > the memory bandwidth.
> >
> >> I've been looking at a VMware ESX server.  it's licensed per 2 CPUs.  A
> >> 4 core is the same as a single or dual core in their licensing.  I'm
> >> finding with that, a dual quad core is cheaper then adding ram + 1 cpu
> >> to 2 systems with 3 single core cpus between them.
> >>
> >> Those 1.6GHz CPUs might use less power & generate less heat.
> >
> > "might" being the key operative word here.  Check the specs.
> >
> >> The real limit on your application will likely be I/O.  Bus speed (FSB),
> >> network, disk speed, memory speed, etc.  How much data are they moving
> >> around? More RAM will help more then CPU GHz also.
> >
> > Keep in mind the memory bus issues.  In particular looking at Intel vs
> > AMD Quad-cores, the Intel quads are effectively two Dual-cores in a
> > single package and they share a memory controller, whereas the AMD
> > quads will theoretically each have a memory controller.  What this
> > means is that you get higher memory throughput (and lower latency) on
> > AMDs than Intels.  I just don't know which applications this effects.
>
> I've always liked the AMD architecture because of their "hypertransport
> bus", which is basically a fancy way of saying that certain things a
> dedicated bus.  Intel's architecture (unless something has recently
> changed) still has everything going through the front side bus.  AMD's
> processors have a memory controller integrated on each processor itself,
> along with a dedicated bus to the memory it uses.  So, you may need more
> sticks of ram, but in theory the bus architecture is highly optimized
> (the memory bus won't be affected by what's going on with the network,
> HDDs, etc).
>
> For a single-user environment, it seems like benchmarks more or less
> prove that the different isn't huge, but i could see how with 50 users
> each doing their own thing AMD's approach may work better.  That's
> purely a (somewhat) educated guess, it might not be true.
>
> As a side note, i know xeon heatsinks are screwed into the motherboard
> for a nice solid connection, but all the other intel chips use what i
> think is the worst idea ever conceived for a heatsink clip.  AMD's
> heatsink fastening system feels so solid when you clamp it down, whereas
> all the non-xeon heatsinks are kind of screwed in with cheap plastic
> gadgets that everyone seems to have problems with.  This doesn't really
> pertain to this issue since we're talking xeon, but i've never quite
> been able to get over that... :-)

Unfortunately the company I'm doing business with only works with Intel 
products.  We used to be an AMD only shop, but I really like doing business 
with this particular company.  The customer support is the most important 
thing at the end of the day!

> > -derek
>
> -chris
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-- 
Warren Luebkeman
Founder, COO
Resara LLC
1.888.357.9195
www.resara.com