Still one more question about AMD processors

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Me and Paul were having this discussion. (Quoted text is Paul's) But it seems
Paul is busy today... or maybe I made a complete fool of myself, but I still
don't understand. My question is at the very end of the text, but following
the discussion might help.

I would like to thank Paul for all the information he's provided so far.


 > Cool N' Quiet is a feature of Athlon64 processors. When Windows
 > is idle, the "CPU driver" can write a FID (frequency) control
 > register, and drop the processor from 2400MHz, to 1000MHz. Since in many
interactive (web surfing, email) situations, the
 > processor is idle most of the time, this saves electricity
 > and makes the processor run cooler.  It immediately speeds up
 > as soon as you move the mouse.

It seems there's also a driver for Linux 2.6.10 and later kernels:

AMD Turion™ 64 Mobile Technology Processors,
AMD Opteron™ Processors, and
AMD Athlon™ 64 Processors Driver Version 1.60.01 for Linux 2.6. - Supports all
AMD Turion™ 64 Mobile Technology Processors, AMD Opteron™ Processors, and
Athlon™ 64 Processors released through 2006. Provides support for AMD
PowerNow!™ technology and, where appropriate, AMD’s Cool-n-Quiet™ technology
for Linux systems. Works with all kernels, version 2.6.10 or later. Requires
cpufreq-1.20, cpuspeed-1.20.1, or powersaved-0.8.19 or later to support SMP
and dual-core systems.,,30_182_871_9706,00.html

So, the same processor may run at different wattages. OK.

 > When the processor is running at full speed (say you are shrinking
 > a DVD before writing a movie to a blank DVD), then the power difference
 > between the high power and low power processors takes
 > effect. Maybe if you kept your processor busy all the time,
 > the lower power rated processor would give you a cooler running
 > computer. But for interactive style usage, the Cool N' Quiet feature
 > saves plenty of power.

I see... but I'm afraid I'll have a question below.

 > As an example, look at PDF page 17 of this document. It shows the processor
 > ADA3500DEP4AS, a 3500+.
 > The allowed operating conditions, tested at the factory are:
 > Name                     Power Frequency
 > Max Pstate               89W   2200MHz
 > Intermediate Pstate #1   69W   2000MHz
 > Intermediate Pstate #2   50W   1800MHz
 > Min Pstate               22W   1000MHz

Ok. Now, here's the SAME processor at:

Processor:         AMD Athlon™ 64
Model Number:         3500+
Frequency (MHz):     2200
L2 Cache Size:         512KB
Socket:         AM2
Stepping:         F2
Manufacturing Tech (CMOS):     90nm SOI
Wattage (W):
System Bus (MHz):     2000

As you can see, there's nothing beside Wattage. At this stage, the choice is
between 35 or 62. Isn't this to operate at 2200 MHz, the maximum frequency?

Re: Still one more question about AMD processors

Quoted text here. Click to load it,,30_182_871_9706,00.html
Quoted text here. Click to load it
Quoted text here. Click to load it

Hi, I am not sure precisely what you are asking (I take it English is not
first language), but anyway....
What puzzeled my  when looking at that processor was that you see two
processors which are identical in everyting apart from power consumption.
Well there is a slight voltage difference but not enough to explain the
power consumption figures.
It just seems they are tested for power consumption and then graded
in a similar mannner to how processors are rated for speed.

            AMD Athlon™ 64 Details
            Processor AMD Athlon™ 64
            Model 3500+
            Ordering P/N (Tray) ADD3500IAA4CN
            Ordering P/N (PIB) ADD3500CNBOX
            Operating Mode 32/64
            Stepping F2
            Frequency 2200Mhz
            HT Speed 2000
            Voltage 1.20V/1.25V
            Max Temp 78°C
            Thermal Power 35W
            L1 Cache 128KB
            L2 Cache 512KB
            CMOS Technology 90nm SOI
            Socket Socket AM2

      Processor AMD Athlon™ 64
      Model 3500+
      Ordering P/N (Tray) ADA3500IAA4CW
      Ordering P/N (PIB) ADA3500CWBOX
      Operating Mode 32/64
      Stepping F2
      Frequency 2200Mhz
      HT Speed 2000
      Voltage 1.25/1.35/1.40V
      Max Temp 70°C
      Thermal Power 62W
      L1 Cache 128KB
      L2 Cache 512KB
      CMOS Technology 90nm SOI
      Socket Socket AM2

Re: Still one more question about AMD processors

Bazzer Smith wrote:

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I didn't think my english was that bad :) I will reformulate my question.

"Is the Ahtlon 64 expected to work at 2200 MHz with 35 or 62W?"

And the answer is in the link you provided:


The answer is no. 35 and 62W are "the power you have to design the cooling
solution to dissipate". As a processor with Cool and Quiet shouldn't work at
full speed all the time, the cooling solution doesn't have to be adapted to
maximum wattage.

OTOH, if Cool and Quiet is not enabled, the temperature is hot and you do
heavy processing...

Quoted text here. Click to load it

Exactly. That's what Paul explained in my preceeding thread:

"So, to make processors with different wattages, you can sort through
all the chips, and take the ones with low power consumption, and
make those your "low power" devices."

Thanks for your link. It answered my last question.

Re: Still one more question about AMD processors

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Cool and Quiet only lowers the CPU speed when the CPU is 'idle' or when it
doesn't need to run at full speed, however there will be times when it will
run at
full speed, so your cooling system must be able to cope with this other wise
risk damaging the chip.

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But even with it is enabled it will still run at full speed when it is doing
a CPU intensive
task so your cooling system must allow for this anyway.

Quoted text here. Click to load it

Yes that puzzled me untill I found that link, the question is do you want to
pay more
for a low wattage chip? It depends on the price differential I guess, but
low wattage
has two advantages, it uses less power and it means your PC will be quieter,
so I would
get one unless the price was excessive.Another advantage is that I expect it
would overclock

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Re: Still one more question about AMD processors

Bazzer Smith wrote:
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Heat transfer rate, or heat flow per unit time, is labeled:


to indicate a change per unit time. It is measured in watts.

So heat dissipation in watts might be unrelated to the CPU's wattage.

Re: Still one more question about AMD processors

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I think the CPU's wattage is determined by the ammount of heat it dissapates
(at full load).
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Re: Still one more question about AMD processors

On Thu, 03 Aug 2006 22:38:58 -0400, Yugo

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It is absolutely IMPERATIVE  that the heatsink, cooling
solution as a whole be able to dissipate maximum wattage.

The design is clearly defective if it cannot, and there
should be a lawsuit to rectify the situation if the builder
doesn't volunteer to do so.  There is no grey area here at
all, it is absolutely necessary for the cooling to handle
full load continuously in the highest ambient temp the
system is spec'd to tolerate.  When no ambient temp spec is
provided, unless noted otherwise we can assume that temp is
roughly 25C, the typical average room temp in a climate
controlled environment.

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What goes in must come out.  The heat is directly related to

Re: Still one more question about AMD processors


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The 35W and 62W for the two processors, are when the processors
are running at 100% load. They will draw less power when idle and
Cool N' Quiet is being used. I had hoped to find a document with
details as to the power at different frequencies, but AMD hasn't
released that document for AM2 yet.

When it comes to the use of electricity, it all eventually
gets converted to heat. I'm going to draw a magic black box (say
there is an electric kettle inside). Now, if the box stores
neither potential nor kinetic energy, then when the electric
power goes into the box, it all has to come out as heat.

          I=10 amps      +-----------+
   V=120 --------------->|   magic   | ~~~
    volts                |   black   | ~~~ 1200W of heat
         --------------->|    box    | ~~~

The 35W and 62W processors will dissipate 35W and 62W of heat
respectively. They will need a heatsink and fan good enough
to remove those amounts of heat energy. The fan on the 62W
processor, will be spinning a bit faster and moving more air,
to maintain the processor at the same temperature.

(In fact, when digital signals flow from one logic device
to another, they carry a small amount of power as well. The
power is dissipated in the device receiving the signal and
other places as well. These effects are small and I choose
to ignore them, for the purposes of this explanation.)

For a basic CMOS logic gate, the formula for power dissipation is:

     P = F*C*V1*V2

F is the frequency that the output moves at (engineers call it
the "toggle rate"). C is the capacitance (charge holding ability)
of the structure on the output of the gate. V1 is the supply voltage
for the gate (1.2V for the processor below). If the output signal
of the logic gate is the same voltage as the supply, then V2 will
be 1.2V as well. If the height of the signal (amplitude) is smaller,
then the V2 value would be smaller. Since for a lot of circuits,
V1 and V2 have the same numeric value, the equation can be written
in slightly simplified form:
     P = F*C*V_squared

Now, we plug in some numbers. The CPU is millions of gates, so
this is sort of a composite example, adding the contributions of
the millions of gates together.

         Frequency 2200Mhz
         Voltage 1.20V/1.25V
         Thermal Power 35W

     35W = 2200*10**9 x C x 1.2V x 1.2V

Well, in this case, we don't know the value of C, it is a constant
of proportionality for all we know, in a black box sense.

Now, say I am an overclocker. I turn up the frequency above 2200.
To overclock, usually I need a little more voltage as well. The
result is the power increases faster than linearly, due to the
voltage increase. At least with that formula, you can see some
of the elements that go into determining how much current and
voltage are used, and the resulting power dissipated as heat.

Now, we'll try another experiment. I'm going to draw
a basic storage element. All this thing is doing right now,
is updating the output on the rising edge of the clock,
so there is logic 1 on the second cycle of the output and
a logic 0 on the third cycle of the output.

   ___1___                                     ___1___
 _|       |___0___| +--------------+  ________|       |___0___|
          ----------| DATA  Output |-------------
                    |              |
                    |              |
          ----------| CLK          |
   ___     ___      +--------------+
 _|   |___|   |___|

This storage element could be considered to be 100% busy, because
it cannot move its output faster than the diagram above. The
state can only change on each rising edge of CLK.

Now, if this thing was hooked to Cool N' Quiet, we could change
the frequency of the clock signal from 2200MHz to 1000MHz when
the computer is idle. Based on the formula above, the computed
power drops by at least 1000/2200 = 45%.

Now, I'm going to reduce the work the storage element is doing.
I'm going to connect a "flat" signal to the storage element.

 __________________ +--------------+  ____________________________
          ----------| DATA  Output |-------------
                    |              |
                    |              |
          ----------| CLK          |
   ___     ___      +--------------+
 _|   |___|   |___|

The above F*C*V_squared equation actually takes as the frequency
value, the frequency of the output. In my first example, if the
clock was 2200MHz, the output would be moving (toggling) at 1100MHz.

Now, in the second example, the output isn't moving at all. So
when the CPU isn't doing any work, it doesn't dissipate any power!
Sounds wonderful. But if we measure the actual power in the lab,
it is about one tenth of the "full power value". The storage
element has multiple logic gates inside, and some of the gates
are connected to the CLK line, and they do work as long as the
CLK is running. So, the electricity flow has not stopped.

So, what can we conclude from this poorly constructed analogy ?

1) When the computer does no useful work (no information is
   flowing through the functional units, so the functional
   units are idle), the power should drop to zero. But since
   parts of the circuits are still wiggling their signals,
   power is still needlessly wasted. That is the nature of
   this particular kind of storage element. There are other
   kinds, but they are harder to work with.

2) So, now we know, that if the computer is idle, it will still
   be burning up some power. (There are many kinds of defects in
   processors that waste power, but I'm not going to explain
   them, as it distracts from the simplified principles.)

3) But if we drop the CLK frequency at the same time, the amount
   of power used, drops to 45% of its former value.

In terms of the above logic gate power formula I have been
abusing, what can we say about the 35W and 62W processors.
Yes, the voltage is slightly different. I'll ignore that
for a second. We never really discussed "C" the proportionality
constant. We could say that the 35W processor has a lower
value of C than the 62W processor. That would account for
some of the difference between the processors. The voltage
drop of a fraction of a volt, also accounts for a small
percentage as well.

Now, I don't expect this explanation will serve any useful
purpose, but it is my attempt to explain when and why a
processor draws power, and all the power it draws is
converted into heat.


Re: Still one more question about AMD processors

Paul wrote:

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Then, why do we have:

 > Name                     Power Frequency
 > Max Pstate               89W   2200MHz


As for the rest, it's hard for me to follow with no knowledge whatsoever in
electronics, but you had a second of inattention here:

Quoted text here. Click to load it

It should be 1200/2200 = 54%

Thanks again for your effort, it might help some other people on this group.
But, for me, try to keep your informations real fundamental.

Thanks to all for answers on processors.

I would like to thank everybody, mainly Paul, then Bazzer, for the answers I
received to my questions about processors. I'm still far from a processor
expert, but the knowledge I gained here in very little time I couldn't have
obtained on the net unless I had spent weeks on research. I'm afraid I
wouldn't have done that.

It's sad, but magazines such as Tom's Hardware seem to always take for granted
that their readers have good basic knowledge of hardware. I'm afraid they lose
a lot of readers this way. 10 years ago, magazines took more pain to explain
the basics.

If Paul wanted to write a page on processors on his site, I'm sure many people
would pay a visit, mainly if there were pages on other pieces of hardware:
monitors, power supplies, etc. No testing, just the basic concepts. But it's
important to keep it simple. Concentrating on the Athlon 64 3500+ has helped
me to learn notions that would also apply to other AMD processors.

Thanks to all again. I received a good demonstration of the usefulness of usenet.

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