i dont know if this is old news, current news or not even news at all, but i figured id share it. this is a featured article in "InfoWorld". im sure you know who they are.... btw intel or amd... i dont care b/c they dont care about me...

DOUBLE VISION -- that's how Intel describes the next
generation of Xeon processors. But with all due
respect to Foreigner fans, it has absolutely nothing
to do with the '70s rock tune of the same name.
Rather, what Intel is alluding to is the new
hyperthreading architecture that graces its latest
server processors.

With hyperthreading, Intel effectively replicates many
of the internal components of the Pentium 4 micro
architecture, creating a virtual image of a second
processor running within the same silicon. Through a
clever manipulation of the CPU's internal
"architecture state" (the contents of various control
registers and external interfaces), a hyperthreading
CPU can execute two unrelated code paths in parallel,
with instructions from each path vying for resources
in a shared execution core.

Of course, there isn't really a second CPU; it just
looks that way to the operating system. In fact, the
illusion is so complete that when you first power up a
hyperthreading-enabled system, the BIOS POST (Power-On
Self Test) reports the total number of virtual (as
opposed to physical) processors. And as goes the BIOS,
so does the operating system. Case in point: Microsoft
Windows. When booting to Windows 2000 or XP on our
state-of-the-art Supermicro P4DC6 dual-Xeon DP test
bed, we found that the OS was completely fooled by the
virtualization scheme. Windows Device Manager
dutifully reported the presence of four 2GHz Xeon
CPUs, despite the fact that the system sported just
two physical processors.

Two heads are better than one

Fooling the OS is one thing. Wringing more performance
out of an otherwise unmodified processor core is a
little more difficult. Intel says that customers can
expect a boost of 10 percent to 30 percent, depending
on the application type, thanks to the more efficient
use of core resources by the dual virtual CPUs, which
are treated as separate processing units by SMP
(symmetrical multiprocessing)-aware operating systems
such as Windows 2000 and XP.

Our own testing shows that Intel's projections are in
fact quite conservative. For example, when serving SQL
transaction data to a series of Windows 2000-based
clients, our hyperthreading-enabled Xeon DP test bed
delivered round-trip throughput an average of 46
percent faster than the same system with
hyperthreading disabled (a simple BIOS switch controls
the feature). Likewise, when we ran a similar scenario
using a Web-based, three-tier application simulation
we saw a boost of more than 31 percent when we enabled
hyperthreading. (For our test methodology, see
"Hyperthreading Xeon DP: How we tested," right.)

To put these numbers in perspective, you'd need to
increase the core frequency of the CPUs by greater
than 1GHz to match these results using
nonhyperthreading processors. We know this because the
very same scenario executed against a similarly
equipped (in terms of peripheral components) dual 1GHz
Pentium III server delivers results that are 34
percent slower than our 2GHz Xeon test bed with
hyperthreading disabled.

If an extra 1GHz yields a 34 percent improvement in
database server throughput with traditional (i.e.,
nonhyperthreading) CPUs, it seems clear that, as an
on-chip throughput enhancement, hyperthreading is
delivering performance on a scale that transcends mere
clock frequency. Hyperthreading represents a potent
combination of parallelism and pipeline efficiency
that will give Intel a huge leg-up on the competition
as it expands the technology to encompass the range of
Pentium 4 derivatives.

Brass tacks and road-worn rubber

Ironically, it is on the issue of where and how they
plan to introduce hyperthreading that Intel is being
the most reticent. Outside of the newly introduced
Xeon DP and MP chips (the former is the one we tested;
the latter includes a large Level 3 cache to support
four-way and higher SMP platforms), there are no
publicly announced plans to incorporate the technology
in any other products. Intel's official position is
that hyperthreading is a server-only technology, and
the company is asking Xeon OEMs not to allow
hyperthreading to be turned on in desktop and
workstation BIOS code.

Although Intel is discouraging speculation about
hyperthreading's role in future desktop or workstation
solutions, clearly this is a technology that is
destined to permeate the very fabric of Intel's
universe. As for why Intel is focusing exclusively on
servers with this initial release, we can only
speculate that it is trying to manage customer
expectations. After all, not every application will
benefit from parallelism at the CPU level, and the
last thing Intel wants to do is to hype a concept that
might confuse the nontechnical masses. Add to this the
ubiquitous "compiler updates" from the various tools
vendors (to fully optimize application code for
parallelism, etc.), and you can see why Intel is
taking it slow.

Finally, no story this compelling would be complete
without a bit of controversy. In the case of Intel's
new Xeon CPUs it has to do with defining what is and
what is not a processor. As we noted earlier,
hyperthreading fools the operating system into
thinking that there are twice as many processors as
there are physical CPUs. In fact, Intel is counting on
this behavior because it needs the OS to schedule
tasks in a way that can exploit the parallelism that
hyperthreading provides.

The problem is that many server products are licensed
based on the number of processors in the system. So if
you're a software vendor such as Microsoft, and you
offer per-CPU licensing as an option for your flagship
SQL Server product, how do you price your product when
the customer plans to deploy it onto a hyperthreading
server? Conversely, if you're a Microsoft customer,
and you deploy the software onto a hyperthreading
server with two physical processors, how many CPU
licenses do you need to buy? And will the software
even run properly if the number of licenses no longer
matches the number of processors reported by the OS?

These are just some of the thorny issues that Intel
will have to sift through as it attempts to translate
technical capability into practical reality. A strong
market demand (you can never have too much CPU power)
should force the software vendor community to get its
licensing house in order. Until then, our advice is to
proceed with caution. The performance advantages are
undeniable, and depending on how the pricing models
catch up with the technology, there may be no excuse
for investing in anything but hyperthreading-capable servers.


Randall C. Kennedy is director of research and
co-founder of Competitive Systems Analysis.

....the birds seemed to be calling him, thought caw....

Nice. Very nice. The 46% improvement is pretty typical of database servers with hyperthreading. No longer will the processor have to wait on hard drive I/O. It can now move on to the next thread while the hard drive does its thing.

-Raystonn


= The views stated herein are my personal views, and not necessarily the views of my employer. =

This looks great - especially on the application server side. It would be perfect if Tom's would do a review on both Xeon and P4 SMT, testing Desktop, Workstation and Server apps under Win2K and WinXP. This would let us know the majority of advantages and disadvantages of Hyper-threading.

I thought a thought, but the thought I thought wasn't the thought I thought I had thought.

this SMT?hyperthreadng is quite useful for the server applications, I dont think its too useful for desktops. it should actually bring down the performance by a bit.

<font color=red>Nothing is fool-proof. Fools are Ingenious!</font color=red>

Yup, that's why I'd like to see some tests.

I thought a thought, but the thought I thought wasn't the thought I thought I had thought.

Raystonn, you mentioned SMT can be turned on with some P4 motherboards. Do you know which ones?

<font color=orange>Quarter</font color=orange> <font color=blue>Pounder</font color=blue> <font color=orange>Inside</font color=orange>
Don't step in the sarcasm!

I do not remember, sorry.

-Raystonn


= The views stated herein are my personal views, and not necessarily the views of my employer. =