Hey Tench.. you had to read the rest of the Register article I think to get where Watson was coming from.. tho I'm not sure I'd draw the same conclusion about Intel being in trouble.. but it was amusing to read this - the hardware sites are already starting to have a field day over this particular story.
Old trick aids Intel in 1GHz
notebook spin
By: Mike Magee
Posted: 21/03/2001 at 16:16 GMT
Intel's SpeedStep technology allowed it to intro a
1GHz Pentium III mobile this week, beating AMD to
the coveted speed tag.
But the jury is out on just how much chips used in
high end notebooks really can be truthfully described
as running at 1000MHz.
Intel's SpeedStep (GeyservilLe) technology goes
head-to-head against technology from AMD
(PowerNow) and Transmeta (LongRun). All are
techniques to control power consumption in mobile
microprocessors and so let the battery last longer.
Via also has a system for the few fanless mobile
CPUs it flogs.
But, according to one source, whether an Intel
notebook is plugged into the mains or running on its
battery, it only hits 1GHz for a very short term.
Comparing CPU speed in a desktop with a mobile is
therefore misleading.
He said: "A 1GHz Pentium III mobile is too hot to run
at that speed all the time, so manufacturers need to
"clock-throttle" the chip, which means momentarily
reducing the speed to avoid overheating.
"There is little difference between the various speed
grades since chips running at higher MHz ratings
require much more clock throttling then the lower
speed grades. The scaling is very bad compared to
that of desktops where clock throttling doesn't exist."
< Benchmarking a notebook with a claimed speed of
1GHz and a desktop at 1GHz - and ignoring hard
drives and VGAs because of the innate differences of
these technologies in these platforms - would mean a
huge difference in performance, despite the speed
tag, he claimed.
Other readers of The Register, however, have been
swift to point out the differences between the
technologies from the competitors in this lucrative
neck of the PC woods.
"Unlike all other modern mobile chips from Intel, this
chip is basically a desktop processor with
SpeedStep," one claimed. "It runs at the full desktop
voltage to get to 1GHz, so it's using near to 38
Watts. You'd drain your average laptop battery
pretty fast at that pace. Of course, it doesn't run at
1GHz when it's unplugged unless you disable
SpeedStep, so it's really only a 700MHz chip when
you're on the aeroplane. That's still fast, but the
1GHz is a little bogus."
Another said: "The APM/ACPI part of the BIOS will
slow the clock if the CPU runs hot. That is the same
part of the BIOS which does the SpeedStep thing, by
the way. I'm not privy to any BIOS source code
anymore so I can't tell you if they do this by reducing
the FSB (front side bus) frequency or by fiddling the
multiplier on the CPU.
"The best place to look is probably the chipset docs,
because it is the Northbridge which implements the
STOPCLOCK hardware protocol with the CPU which
makes it possible to fiddle with multipliers and bus
clock rates.
"Most operating systems these days will halt the
CPU whenever they have nothing else to do that to
wait for the next interrupt (keyboard, disk, network,
whatever), that way you can run the CPU at say
1GHz as long as you only do some light work like
typing in a word processor because it really only runs
10 per cent of the time so the thermal output
corresponds to say 300MHz.
"As soon as you throw real work at the CPU,
calculations, reformatting a 100 page doc with a new
template, MPEGs and so on, the CPU will quickly hit
the thermal limit and be slowed down by the
APM/ACPI BIOS so that it can continue to run
without melting the plastic around it.
But, he added: "The battery lifetime issue is a very
good reason for slowing the clock."
Replacement batteries for top-of-the-range
notebooks are often sold by vendors at a hefty
premium to those flush enough to have found $2,500
in their Four Plus pockets*.
But clock throttling is not a new phenomenon in Intel
chips. Far from it, according to one source close to
the development of all former and latter day x86
processors
"Clock throttling was around since the original
Pentium; it was certainly around before Intel invented
SpeedStep, to wit Transmeta responded with
LongRun. Clock throttling was Intel's original form of
controlling power consumption in mobile chips.
"Here's how it works. A 4KHz square wave is applied
to the STPCLK pin of the CPU. Depending on the
duty cycle, a greater degree of clock throttling
occurs. When the square wave is active, the CPU
actually stops executing code and essentially shuts
down (this saves power). As you can see from this
method, the greater the duty cycle of the square
wave, the longer the CPU is inactive; hence the
greater the power savings.
"I believe clock throttling begins at 75% (25% duty
cycle) and goes down to 12.5% (87.5% duty cycle).
"Here's where the fun begins. Guess how Intel
acheived their "1-W CPU" to answer Transmeta?
First, they took their 1GHz CPU from the top of their
yield. Due to yield characteristics, these top of yield
chips also have the ability to run at the lowest
voltages. So, first they robbed their most profitable
chip line to create this chip. Second, they reduced
the frequency to 600MHz and lowered the voltage
down to something like 1.15V. Third, they clock
throttled the thing down to 12.5% utilisation --
thereby creating the performance equivalent of a 75
Mhz Pentium III (600 MHz * 0.125 (12.5%)). Finally,
they sat idle in MS-Word and measured 1 Watt.
That, he said, should be compared with Transmeta,
which can play a DVD at one Watt at full speed,
using LongRun.
It's certain that tier one vendors, a rash of which
endorsed Intel's 1GHz PIII mobile launch earlier this
week, implement the technology in different ways.
Late last year, we saw Toshiba technology which
implemented water cooling in a high end notebook.
A technician at a tier one vendor, who didn't want him
or his company to be named, said: "I was at an Intel
meeting about a year ago where it was explained
that Intel marketing didn't like the term throttling, and
changed it to thermal management." ®
theregister.co.uk |
