Q: What’s new and different in Intel’s Q: What’s new and different in Intel’s
new CPU?
The really big news with Prescott is the
shift from the current 0.13-micron or 130-
nanometer process Intel has been using for
the Pentium 4 since the second-generation
Northwood version was released in 2001 to
a new 90-nanometer process. This new pro-
cess gives Intel a few advantages besides
the ability to cram more transistors into a
smaller space.
Anytime you shrink the size of the cir-
cuits in a CPU, you also shrink the distance
electrons must travel to get from point A to
point B. Consequently, less voltage is used,
which creates less heat. This means the
CPU can run at higher clock frequencies.
Intel’s original 1.5GHz Pentium 4, code-
named Willamette, ran hot because it used
a 180-nanometer process. As a result,
the CPU didn’t overclock very well and
ran out of gas at 2GHz. Shrinking the die
to 130 nanometers allowed Intel to run
the Northwood all the way from 2GHz to
3.4GHz with no end in sight. Shrinking the
die to 90nm will greatly benefit Intel’s—and
perhaps consumers’—bottom lines as it
will substantially reduce production costs.
But beyond the die shrinkage, Intel has
tinkered quite a bit with Prescott’s actual
core. The biggest enhancements include:
13 new instructions called SSE3, double
the amount of both L1 and L2 cache (16KB
and 1MB, respectively), and a new pipeline
with a whopping 31 stages. Better thermal
protection and enhanced Hyper-Threading
are also included.
As a CPU core, Prescott has changed
significantly from the Northwood, much
more so than the jump from the original
Willamette P4 to Northwood. All told, the
Prescott is quite a different beast indeed.
The result will be hockey-stick style perfor-
mance increases as the CPU’s clock speed
is boosted and applications become more
capable of using the new instructions and
extended pipeline.Q: Are the rumors true that dormant
64-bit support extensions have been
tucked into Prescott?
Despite many rumors circulating on the
Internet, Intel has continued to publicly
deny that 64-bit extensions are hidden
in the Prescott, and insists that its server-
based Itanium CPU is the company’s only
64-bit processor. So we asked the company
point-blank: Does Prescott contain 64-bit
extensions? Intel refused to comment, but
the company did take the opportunity to
diss AMD: “For us to enable such a thing
in an Intel volume mainstream processor,
we would need to validate the design with
a production mainstream operating system
with a wide variety of device drivers in the
client space. That isn’t here today.”Herein lies AMD’s 64-bit conundrum.
Microsoft still hasn’t released its 64-bit ver-
sion of Windows, and—at least according
to reports we’ve heard—porting Win XP
drivers to the beta 64-bit is turning out to
be far more challenging than AMD original-
ly indicated. (For more on AMD’s strategy,
turn to page 35).Q: What instructions are in the new
SSE3 set and how can I take advan-
tage of them?
SSE gave us 72 instructions that program-
mers could use to enable applications—
particularly games and multimedia—to
run faster. SSE2 gave us 144 instructions
for handling multimedia, gaming, and
floating-point and integer conversions.
In contrast, SSE3 gives us just 13 new
instructions. Despite its fewer instruc-
tions, the goals mostly remain the same
as before: better floating-point and integer
conversions, and faster video encoding.
There are also new instructions for better
synchronization of application threads.
As always, you won’t experience any
immediate benefits from the new instruc-
tions. Existing applications will have to
be either patched or recompiled to take
advantage of SSE3. Intel couldn’t provide
any applications that supported SSE3 at
press time, so we found it difficult to mea-
sure their effectiveness. In the past, how-
ever, special instructions have made quite
a difference. For example, if you were to
compare a 450MHz Pentium II to a 450MHz
Pentium III with SSE, you’d find that the P-II
lays bricks compared with the P-III in MP
encoding. So, to some extent, you do get
more performance by buying instructions
that you won’t be able to use for 12 to 24
months. On the other hand, why pay a pre-
mium for new instructions that you won’t
be able to use for 12 to 24 months?Q: What are the benefits of the
31-stage pipeline and what are
the penalties?
When the P4 first came out with its (then)
phenomenally long 20-stage pipeline,
we wrote: “Long pipelines are inherently
friendlier to high clock speeds.”
An analogy will help explain this state-
ment: A CPU’s pipeline is much like a car
factory’s assembly line. Over at the Athlon
XP factory, which has 10 stages (that is,
10 assembly line stations), each worker at
each station is assigned a relatively large
amount of work. For example, a single
worker might put on a hub cap, screw in a
dashboard, and install windshield wipers—
and all this work must be completed before
the unfinished car can proceed down the
line. Because only one worker can attend
to the car at any given time, the assembly
line moves only as fast as the ËQ: What’s new and different in Intel’sQ
Q: What’s new and different in Intel’s Q: What’s new and different in Intel’sQ
Q: What’s new and different in Intel’s
new CPU?Q
new CPU?
The really big news with Prescott is the
Q
The really big news with Prescott is the
shift from the current 0.13-micron or 130-
Q
shift from the current 0.13-micron or 130-
Q
Q: Are the rumors true that dormantQ
Q: Are the rumors true that dormant
64-bit support extensions have beenQ
64-bit support extensions have been
tucked into Prescott?
Qtucked into Prescott?
QDespite many rumors circulating on the Despite many rumors circulating on theQ
Q: What are the benefits of theQ
Q: What are the benefits of the
31-stage pipeline and what are
Q31-stage pipeline and what are
the penalties?
Q
the penalties?
When the P4 first came out with its (then)
Q
When the P4 first came out with its (then)Q
Q: What instructions are in the newQ
Q: What instructions are in the new
SSE3 set and how can I take advan-Q
SSE3 set and how can I take advan-
tage of them?
Qtage of them?
QSSE gave us 72 instructions that program-SSE gave us 72 instructions that program-