
With all the fuss about the enormous power losses oozing from the Pentium 4 Prescott, there's little word about the power needs of AMD's processors. Of course, Cool and Quiet means that the 64 bit processors can be slowed down if needed and thus rarely become really hot. No modern desktop processors are really easy to please, however. Unless, of course, you are prepared to accept unusually low clock speeds.
All told, in fact, a processor speed that is slower than 1 GHz is more than enough for surfing the Web, running standard office applications and performing simple audio/video tasks. It's thus no accident that mobile processors reduce the work cycle at low load for these tasks.
Indeed, there are also numerous applications where performance is not the most important factor. Intel, for example, dreams of the "digital home," yet only delivers components that would last long without active cooling controls. So why does a media center designed for living-room use need to burn up 100 watts and then make a racket with its fans to boot?
Around 800 MHz, for example, is sufficient for entertainment needs, as tests with an Xbox showed. Here we mean playing Full-PAL videos in MPEG-2, DivX or XviD. And MP3 audio makes less demands anyway. However, if you require real-time encoding for fast video recording, you will need more pizzazz. Slower PCs are also useful as network slaves, taking on the functions of file and print servers, routers or access points, for example. These are usually in operation round the clock, so the quieter the better.
AMD's AthlonXP and the Sempron make perfect guinea pigs for this project, which essentially involves tricking the BIOS to make the processors run like a mobile AthlonXP. This involves opening the multipliers , which only these processors allow.

IPCop is freely available, Linux-based software that combines all important network services, including routing. A DSL router can thus be dispensed with, as both the range of functions and handling is much higher with these software solutions - and performance stays spot on thanks to a fully-fledged processor.
The permanent quest for more performance is what largely sustains the PC and components industry. However, as we mentioned above, maximum performance is not necessary for all applications. A majority of users these days run demanding applications that are primarily greedy for RAM. Typical applications for mid-range computers (running on Windows or on Linux) include storing and playing audio and image files.
The file server in the corner only needs a couple of hundred megahertz, toos - print and simple network services rarely require more to accommodate a reasonable number of clients.
While we're on the subject of network services, we should also mention routers. As a rule, stand-alone devices are used that may match up to DNS and DHCP servers, but only rarely have the muscle to make a large number of connections. The large peer-to-peer networks such as Emule and Bittorrent rely on a large number of connections in order to allow many users to exchange data as quickly as possible.
Meanwhile, the bottom line goal is for the PC to run as economically as possibly at all times. It should also be possible to control clock speeds and hence performance and power loss if necessary. This is precisely the option you have with a modified AthlonXP.

Just like the desktop version, the Mobile AthlonXP has mostly open bridges on the top that are responsible for switching special functions on and off.
Although the Desktop AthlonXP package is far larger than its mobile counterpart, both processors basically have the same L-Bridges on the top. In the mobile version (see above), the bridges for the multiprocessing and mobile modes are closed. The same must of course be performed on the desktop version to achieve the same results. The bridges are closed by using a suitable electrical conductor - in our case, conductive silver lacquer.
However, only a few motherboards recognize the modified processor, because of course the Mobile Athlon was never designed for a Socket A system. Setting up the CPU information can therefore be considered the hard work of the mobo makers. We made out well in our tests with the MSI KT880 Delta and Abit KV7.

That's how a "real" Mobile AthlonXP in a standard notebook is recognized.

The MSI KT880 Delta recognizes the modified AthlonXP correctly as an AthlonXP-M.

The control panel also confirms what CPU-Z had already diagnosed correctly: an AthlonXP-M.


Another diagnostic tool that can calculate the CPU speed
What You Need
The task at hand is to close two bridges left open at the factory so that we can activate the desired functionality. As it is no disadvantage for the processor to be recognized as an AthlonXP-M, you don't need to worry about the permanency of this step. This decision provides an added bonus in the form of the materials to be used: conductive silver lacquer. As soon as it is dry, the bridges are permanently closed, and the CPU does not need to be handled with extra care.
Connecting the pair of pins to unlock the multipliers, as required on the Barton Athlon, was far more complicated since the wire loop quickly comes undone when removing the processor. An alternative to overclocking is offered by a socket adapter, from U.S. manufacturer Upgradeware, for example.
To ensure nothing goes awry when applying the conductive silver lacquer, we need an isolator to seal off the surrounding bridges. Thin adhesive tape is perfect and sticks well to the Athlon's plastic casing.

We chose an AthlonXP 2800+ for the modification.

The bridges for the MP and Mobile Mode are our patients.

The tape should be placed in such a way that only the bridges that need to be closed are accessible.

We make doubly sure and tape on a bit more. After all, the entire construction can be removed in one piece afterwards.

Now we're ready to carefully apply the conductive lacquer in suitably small quantities.

A few minutes' drying time is usually all you need. If you really want to make certain, wait a half-hour or put the processor in a warm place. But, please, not in the sun.

Now the tape can be carefully removed - all that remains are the bridges closed by the conductive lacquer.

The procedure must now be repeated for the second bridge. If you're good at taping, you can of course do both in one fell swoop. Be careful, however, that the painted areas do not touch when applying the stuff.
For further reference, we recommend that you take a look at the second THG video which describes how to unlock the multipliers in the AthlonXP Palomino using the same process.
Web link: THG videos
Video file: download
If you would rather not permanently release the high multipliers, we can recommend the procedure with the complicated, but reversible wire method:
AMD supplies its OEM customers with a tool by the name of PSTCheck (Performance State Check), which can change the clock speed and voltage settings of almost all Athlon CPUs while they're running. As this is a relatively powerful tool, it is not available to end-users.
The multiplier and the CPU core voltage can both be changed on a mobile processor while it is in operation. It is also possible by hand in our case, but then only with the help of the appropriate software. The same methods should also function on CPUs with Cool'n'Quiet support (Athlon 64 for Socket 754 and Socket 939); we had a great deal of trouble in the short tests we conducted, however.
The same is not true of the freshly modified AthlonXP-M: It allowed the multipliers to be adjusted to between x3.0 and x12.0 without a murmur, which, at 166 MHz FSB speed, results in clock speeds ranging from 500 MHz to 2.0 GHz. What is important in connection with low power losses, however, is also to lower the supply voltage, because the 1.65 V powering of the Athlon-XP CPUs is a sheer waste at under 1 GHz. As the power loss is calculated from the product of voltage and electricity (P = U*I), the voltage should therefore be reduced.
Since AMD's PSTCheck software is not freely available, we are usually restricted to those options offered by motherboard-makers in the BIOS or through the capabilities of the used voltage transformer. But the motherboard, too, must fulfill requirements in handling a pseudo-mobile processor.


As the AMD tool PSTCheck is not available, we have to look elsewhere. An ideal choice is CrystalCPUID, a freeware tool that allows you to set multipliers.
With this tool, you set the smallest and largest multiplier. You also need to enter details such as which CPU load (or "threshold") triggers the next higher/lower multiplier. If only one clock speed is required, the same multiplier is used for both the largest and the smallest value.

The freeware tool CrystalCPUID V3.5 to change the multiplier under Windows
To make all this happen, the motherboard BIOS must activate a few registers to provide the required functionality. If this is not the case, the system simply crashes at the very attempt.
| Chipset | Register | Bit/Function |
|---|---|---|
| NVIDIA nForce2* | F6, Bit 4
E7, Bit 4 |
Halt Disconnect
FID_Change Detect |
| VIA KT133A | 55 | Bit 2=1 |
| VIA KT266, KT266A, KT333 | 95 | Bit 2=1 |
| VIA KT333CF, KT400, KT400A, KT600 | D5 | Bit 2=1 |
| *only works on a few boards | ||
Unfortunately, it is only possible to change the multiplier on a few motherboards. One of the fastest, the Asus A7N8X-E, crashed every time we tried.
Multiplier In The BIOS: Boot With What?
As the end-user is mostly also prevented from changing the CPU voltage on the fly (without a reboot), a well-functioning combination of multiplier and CPU voltage must already be selected in the BIOS. What makes this difficult is that most motherboards offer the multipliers x5.0 or x6.0 as their smallest value - none of the mobo-makers offers anything below that.

The MSI KT880 Delta supports the multiplier change during operation and can be started with a minimum 100 MHz system clock, a multiplier of x6.0 and 1.35 V core voltage.
Another option to reduce speed, voltage and thus power loss would be to reduce the system clock to a sensible minimum. The slowest Socket A processors were AMD's Duron models that worked at 100 MHz FSB clock speed using the Double Data Rate method (FSB200). In practice, 100 MHz is thus the lowest settable value.
If only 133 MHz is offered in the BIOS, then you often have the option of using the freeware tool ClockGen from CPUID. If supported by the clock generator on your motherboard it can change the system clock during operation. In connection with CrystalCPUID, and provided you have a suitably equipped motherboard, you can always settle on the minimum clock of 300 MHz (100 MHz system x 3.0).

The MSI KT880 Delta's clock generator is supported by CPUID's ClockGen.

The MSI KT880 Delta allows just a minimum core voltage of 1.375 V.
We already mentioned reductions in the processor supply voltage in connection with low clock speeds. In our test, we were able to operate the AthlonXP stably at 300 MHz with a voltage of 1.375 V (1.65 V is usual for the AthlonXP 2800+). However, a far lower value can without a doubt be chosen safely. At these settings, 100% CPU load (induced by Prime95) produced maximum power loss of approx. 8.1 W; when idle it was just 5.6 W.

Record: Just 4.5 Watts Dissipation

We scored 4.1 amperes on the idle 300 MHz Athlon on a KV7 from Abit.
The change to an Abit KV7 with a KT600 chipset from VIA enabled the choice of just 1.1 V - not many motherboards permit this. The result is heartening: just 4.5 W for the idle processor (1.1 V x 4.1 A). This heat can now be easily dissipated by a passive cooling element.

The Asus P4P800's BIOS offers all the technical means to raise or lower the FSB clock speed.
The slowest Pentium 4 still available is the 2.8 GHz model for Socket 478 based on the Northwood core. Given that the current models work at 200 MHz FSB (FSB800, quad-pumped), these processors also offer the potential to halve clock speed by reducing the system clock to 100 MHz (FSB400). Values below this are not possible, however, since Intel does not release its CPU's multipliers - any number of tools or smart BIOS developers won't change this.
Almost all motherboards offer the opportunity to adjust the FSB clock speed in the BIOS, including Intel's own models. If your BIOS does not support this, you can still fall back on utilities that address the clock generator directly (see above, ClockGen). Less than 100 MHz FSB is not possible, however, which limits the P4 2.8 GHz P4's lowest possible speed to 1.4 GHz. A model with 2.4 GHz and FSB800 can thus be underclocked to 1.2 GHz (multiplier x12).
Due to the binary codes for the core voltage hardwired into the Pentium 4, the motherboard adapts itself automatically to these voltage settings. This means many motherboards do not allow a lower voltage than this, dashing hopes of further cuts in power losses.
What's happening at Intel?
Whoever thought that the P4 Prescott would represent the peak of power consumption ought to know better after taking a look at the Prescott in the Socket 775. The new generation gobbles up even more power.
To counter this questionable development, the next stepping (a development stage in a complex chip) under the codename E0 offers a range of additional features. Thermal Monitoring 2 is thus able to vary the core speed on the fly, according to CPU load, similar to mobile processors, in order to lower average power losses. It's understandable that Intel avoids comparisons with SpeedStep, and thus designates the new function simply as "demand-based switching."

Less than 100 MHz FSB clock (FSB400) is not possible on Intel's Socket 478 systems.
Halving the clock speed did the trick: At just 100 MHz FSB clock the Pentium 4 2.8 GHz in idle mode showed power needs of approx. 8.4 watts. Unfortunately, the power loss under load is still phenomenally high - our measurements with Prime95 showed 31.2 watts at 100% CPU load.

We pitted the 3.0 GHz sample of the P4 Northwood into the running with a x14 multiplier at 100 MHz FSB clock speed.

At a CPU speed of 1,400 MHz, the die temperature clearly cooled to as low as 34.5°C in an open system using the boxed cooler from Intel.

With the help of the ClockGen tool, the FSB can be switched down to 100 MHz during operation.
| Intel Processors | |
|---|---|
| 200 MHz FSB (Dual DDR400) | Pentium 4 2.80 GHz (3400 MHz 12-8/512 kB)
Northwood Core, Socket 478 |
| AMD Processor | |
| 200 MHz FSB (DUAL DDR400) | AthlonXP 3200+ (2200 MHz 128/512 kB)
Barton Core, Socket A |
| Memory | |
| Intel Pentium 4
(Socket 478) |
4 x 256 MB - DDR400 (200 MHz)
Corsair TwinX CMX256A-3200LL XMS32005 V1.1 |
| AMD AthlonXP
(Socket A) |
2 x 512 MB - DDR400
Corsair CMX512-3500C2 XMS3502 V1.1 |
| Motherboard | |
| Intel Platform
(Socket 478) |
Asus P4P800 Deluxe
Intel 865 Chipset Intel 82547EI Gigabit Ethernet Controller (CSA) |
| AMD AthlonXP Platform
(Socket A) |
MSI KT880 Delta
VIA KT880 Integrated Fast Ethernet LPC Abit KV7 VIA KT600 |
| Common Hardware | |
| Graphics Card
AGP |
ASUS V9999 Ultra Deluxe
GPU : NVIDIA GeForce 6800 Ultra, 400 MHz Chip Clock Memory : 256 MB DDR-SDRAM, 550 MHz Chip Clock |
| Hard Drive (AMD System) | Promise FastTrak S150 TX2plus (Bios : 1.00.0.37)
2 x SATA Maxtor 7B250S00 (Raid 0) 250 GB / 16 MB Cache / 7200 rpm |
| Hard Drive (Intel System) | Intel FW82801ER ICH6FR
2 x SATA Maxtor 7B250S00 (Raid 0) 250 GB / 16 MB Cache / 7200 rpm |
| DVD/CD-ROM | MSI MS-8216D 16x DVD |
| Software | |
| Intel Chipset | Chipset Installation Utility 6.0.1.1002
Application Accelerator 4.1.0.6325 |
| Nvidia nForce | Nvidia V4.24 (05/10/2004) |
| Nvidia Graphic AGP | Detonator 61.45 |
| VIA Chipset | VIA Hyperion 4 in 1 V4.51 |
| DirectX | 9.0b |
| OS | Windows XP Professional, 5.10.2600 Service Pack 1 |

The Jet 7 from Coolermaster is one of the more unusual models on the market.
Based on the low power dissipation produced by the Athlon at a few hundred megahertz, passive cooling even becomes feasible. The only prerequisite is a suitably dimensioned cooling element.
Many CPU coolers available on the market offer the option of stepless fan speed settings. We tried some coolers at the lowest and highest possible speeds and with the fan turned off. They were the Jet 7 from Coolermaster, the SLK-800A from Thermalright and Zalman's CPNS 700A-CU. All allowed stepless setting of the fan during operation and are thus perfect for our requirements.

A good-value model: SLK-800A from Thermalright

CNPS 7000A-CU from Zalman

Although the 3DCooler GH-PCU21 from Gigabyte is the latest version, it can't hold a candle to Coolermaster's Hyper 6.

With the Hyper 6, which tips the scale at one kilogram, passive cooling is possible even on Intel systems.

The CNPS 7000A-CU from Zalman once again - it can be used on P4 systems too.

The boxed cooler from Intel is included in the Pentium 4 Northwood package. Meanwhile, a more powerful model with copper core is used for the Prescott processors.
Temperature Readings Of AMD CPU Coolers
Not all motherboards let you throttle back the supply voltage on the AthlonXP to the lowest values. For this reason, we carried out measurements at the usual 1.65 V and at the 1.375 V that represents the minimum achievable on numerous motherboards.

Cooler temperatures at a CPU core voltage of 1.375 V.

Cooler temperatures at a CPU core voltage of 1.650 V.
As long the processor fan is rotating - at whatever speed - all coolers performed to our satisfaction. Particularly when operating at 1.65 V, the fan speed made little difference; the heat sink's design is by far the most important factor. Only at 1.375 V do you have the option of passively cooling your system - but only with the Coolermaster and Zalman models, however. The simple Thermalright is after all a low-cost model.
Temperature Readings Of Intel P4 CPU Coolers

To generate a high processor load, we used the prime-number program Prime95. It enabled us to measure power loss at a great number of speeds.
AthlonXP 3200+ at 100 MHz FSB

AthlonXP 3200+ at 200 MHz FSB

Intel Pentium 4 at 2.8 GHz

AthlonXP 3200+ at 100 MHz FSB

AthlonXP 3200+ at 200 MHz FSB

Intel Pentium 4 2.8 GHz




















Our configuration offers home-made measures to make up for the manufacturer shortcomings. In fact, our modifications took only 30 minutes to complete at a minimum cost and low risk. The result is a processor that, after the modification, is recognized by BIOS as an AthlonXP-M.
The range of functions also gets bumped up: with the help of CrystalCPUID, the multiplier can be freely chosen from all possible values offered by the processor during operation. It also becomes immediately apparent whether the motherboard supports this operation or not. If not, the system crashes and you are left to choose a lower multiplier, FSB speed or CPU core voltage in the BIOS.
If the endeavor is successful, though, the multiplier can then be changed during operation based on your needs. You might choose, for example, full speed when you're working with the system and a low speed when the PC is performing more rudimentary tasks that do not require high processor speeds, such as downloading files. The processor fan can be adjusted accordingly, as we have demonstrated.
The only limitation is the CPU core voltage that cannot be varied under Windows - AMD keeps the corresponding utility under lock and key for security reasons. Thus a compromise between maximum and minimum speed is called for.
It has also become apparent that only a great deal of effort will induce a Pentium 4 to operate passively and deliver full performance. The reason for this is the fixed multiplier, which has been blocked to user access for many years. Only AMD continues to offer the option of changing the multiplier - the Athlon64 models for Sockets 754 and 939 master this. In the future, this type of feature should be doubly welcome because it would keep electricity bills lower and expand the processors' possible uses. And here's exactly where the problem lies - which chip maker will want to let users transform a normal CPU into a mobile CPU, and thereby take a chunk out of their own shares in the mobile market?
