Advice/Suggestion/Info CPU comparison Athlon64 v P4

Hi all,
I've been approved for funding to start a web design and hosting
business. It's a good thing I have gotten assistance as the costs of
startup are higher and the growth of opportunities, i.e. income, is slow in
coming. Anyway, part of what was approved, and I am lucky in this matter
was a computer upgrade of the MB and CPU. Having been using an Athlon XP
1700+, I've had to put on hold some opportunities that my system could not
keep handle, that is unless I shutdown everything else besides one app and
then let it go on its own. But that is the issue of concern in my choice.
I had been thinking that the Athlon64 was the best choice, with the better
performance on 32 bit apps then Intel's 64 bit CPUs. It's been a little
while since I did the Computer Engineering type work and designing systems
but my training was enough to suggest that a Athlon64 versus a Pentium 4 at
the same speed or comparable speeds would show the Athlon64 to be a greater
performer.
Then it was pointed out by a computer dealer who I use often that
since I do multitask that the hyper-threading would be best for me. In
fact I do, as a web designer multitask, in so far as I'd have perhaps,
Flash, Dreamweaver, and Photoshop open at once and other applications in
the background such as an apache server, mysql and php. That I use mainly
to test applications before uploading them.
Anyway, I had thought that I had read that the Athlon XP and Athlon64 both
offered multithreading. In fact it is multitransport on the Athlon64
versus the 32 bit Athlons, such as Athlon XP CPUs. So, I did some research
trying to figure out which would best meet my needs or offer the best
performance in relation to my typical use of the system. Some reports say
that the P4 with Hyperthreading beats the Athlon64 with hypter-transport (
I recognize these are different concepts). So, I could use some advice, or
web links to make informed decisions, to make comparisions... My research
so far has left me vacilating between the best choice being the P4 and the
Athlon64. One factor is the relatively or seemingly small different in
multitasking performance that the P4 might have in any reports I have read,
or reviews. For Streaming media, video editing, audio/video/multimedia or
other I/O issues the Athlon64 at comparable speeds does win out. The
Athlon64 3200 (should there be a + there as in the Athlon XP?) and the P4
3.06GHz. I beleive the onboard memory controller does have an impact on
the I/O because I/O will be going into memory and the access to memory for
the Athlon64 is faster with the onboard memory controller.
Any advice, feedback, refrences to pursue, i.e. web sites, would be
greatly appreciated, along with of course some explanations to clarify my
thinking and understanding,
Thanks,
Bruce
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Bruce Whealton
Triangle Web Hosting and Web Design
http://TriangleWebHosting.biz
or http://TriangleWebHosting.net

++++++++++++++++++++++++++++++++++++++++++++++++++ +++

First to clear up a bunch of misconceptions. Hyperthreading and
Hypertransport are two completely different thing.

Hyperthreading is running multiple instruction streams through a single
processor at the same time. The P4 does this, the Opteron does not.

Hypertransport is a very fast bus that's designed to multiprocessors to
work together effeciently. This is used by all AMD 64 processors, however
the hypertransport buses on the Opteron 2xx series are set up to allow two
Opterons to work together. The Opteron 8xx series can hook up to 8
processors together.

Multiprocessing is multiple real processors. A dual Opteron or a dual Xeon
system is and example.

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Hyperthreading on the P4 doesn't work very well, it boosts throughput by a
small amount (about 10%) but cuts individual thread performance by about
25% (at least it did when I measured it on a dual Xeon system).

The Opterons are much more effecient multiprocessors than the Xeons. There
are several reasons for this.

1) Each Opteron has it's own memory controller. In a dual processor system
that means that the total memory bandwidth available is twice the
bandwidth in a dual Xeon system because the Xeons share a single memory
controller.

2) IO doesn't compete for bus bandwidth in a Opteron system because the
memory is on a dedicated bus. On the Intel processors everything shares
the same frontside bus so memory accesses compete with IO accesses.

3) The hypertransport buses provide a scalable multiprocessor
interconnect, as you add more processors the gain is larger.

The AMD64 CPUs have a much more effecient microarchitecture. The big
advantages are,

1) Much shorter pipelines, about half the length of the Intel processors.
Long pipelines allow for higher clock rates (which is why Intel did it)
but they suffer anytime a branch is mispredicted because more work must be
thrown away. Intel added hyperthreading as a way to get back some of the
performance that they lost by making their pipes to deep.

2) On board memory controllers, these cut down memory access times
significantly.

The only place where the P4 processors are competitive is in games and
other multimedia applications. For server style computing you'll find that
an Opteron system will be much faster.