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 Post subject: P1 to Athlon XP software cooling & Athlon XP CnQ equival
PostPosted: Fri Apr 01, 2005 3:08 pm 

Joined: Sat Dec 14, 2002 7:00 am
Posts: 806
Location: Germany
Athlon XP to P1 software cooling & Athlon XP CnQ equivalent

1. Athlon software cooling
2. Older CPUs - K6, K5, Pentium III/II/I and so on
3. Cool'n'Quiet equivalent for Athlon XP

1. K7 Athlon software cooling

Aka "disconnect on HLT", aka "disconnect on STPGNT" aka "S2K bus disconnect"

Here, the CPU goes sleeping after a special command is recieved. It's the only possibility without hardware modding for a K7 Athlon to save power at idle.
This feature is supported since the very first Athlon/Duron CPUs.

More detailed
When there is nothing to to, the operating system has the possibility to send three different signals to the CPU:
no operation, HLT, STPGNT.
Windows 9x versions without ACPI installed use "no operation".
Windows 2000 and XP without ACPI installed use HLT.
All Windows' with ACPI installed use HLT.
Linux without ACPI kernel support use HLT, with ACPI kernel support they use STPGNT.
There is a Linux-Howto available.

Once the chipset recieves a HLT or STPGNT is disconnects the FSB from the CPU. The CPU now uses a divider (8...512) to clock itself down significantly.

There is no power saving difference between the HLT and the STPGNT command.
Enabling this feature doesn't bring any performance hit, as showed in this arcticle under "Heat Dissipation".

Chipset support

VIA - Best compatibility. Works flawlessly on my KT133,KT266a,KT333,KT600. Supports disconnect on STPGNT, supports disconnect on HLT since the KT266.

Nvidia - Nforce supports at least disconnect on STPGNT. Nforce2 supports disconnect on HLT. But only some boards are working - the others are getting instable. Search for experiences on your favorite board on google.

SIS - ECS K7S5A does not work. But chipsets generally support it.

Have a look in the Linux-Howto in order to find out wether your board supports the feature. If it says "works without ACPI" it also disconnects on HLT.

How to enable

Athlon XP mainboards supporting software cooling directly through the BIOS

You have to look for "S2k bus disconnect" in you BIOS.
According to
ASUS A7V8X v1.04
Gigabyte GA-7VAXP v1.0
Gigabyte GA-7VAX v1.1 (one SPCR user could not confirm this)
Gigabyte GA-7VA v1.0
(all are KT400) should have implented this.

In the forum the Abit NF7-S v1.4 was confirmed.

Abit NF7-S v2.0 (nforce2) and
MSI KT3Ultra (KT333) confirmed here at SPCR

MSI KT6 Delta (KT600) confirmed by my myself
Albatron KX18DS Pro Nforce2 Ultra confirmed at

Via 3rd Party Software

Now your BIOS does not support the feature. All you have to do now is to find a software which changes some registers in the north- or southbridge of you motherboard and thus enabling the disconnect.
S2kCtl - it's free and has the options to alter the divisors. Still developed, should support many mainboards.
CoolOn - freeware, supports VIA, SIS, nVidia chipsets. Option to alter the divisors.
Vcool - it's free but it's developing very slow. It supports VIA boards until the KT400. There is no option to change the divisor, but options to change some PCI settings which is good for troubleshooting.
CPUIdle If the the freeware does not work, try this shareware. Should support every chipset.

Special case: Windows 9x without ACPI and chipset only supports STPGNT but operating system sends HLT
You need a software which overrules the system idle thread with a new idle thread.
Vcool issues STPGNT signals. With CPUIdle one can select between HLT ("S1 state") and STPGNT ("C2 state"). RMClock issues HLT.

Powerusers: WCPREdit
With this program you can edit the registers of your northbridge interactively. It's good for looking behind the scenes or if you are not satisfied with the other programs. It's good to get a .pcr file for your chipset. George Breese has some for Via chipsets.
But it also works without the pcr files. Just go to the Linux-Howto and have a look at the setpci commands:
enable: setpci -v -H1 -s 0:0.0 52=$(printf %x $((0x$(setpci -H1 -s 0:0.0 52) | 0x80)))
disable: setpci -v -H1 -s 0:0.0 52=$(printf %x $((0x$(setpci -H1 -s 0:0.0 52) & 0x7f)))

The interesting part is in the end of the first line. It says: for register number 52 you have to apply a bit-wise OR with 0x80 or 0b10000000. In order to change it back look at the second line: you have to apply a bit-wise AND to register number 52 with 0x7f or 0b1111111.
One drawback of WpcrSet: after S3 standby mode, the bit is not set on my MSI KT266 Pro2.

Once you've enabled the disconnect listen to some music from you PC and try to create a large RAR-archive in order to test wether your PC is stable.


Ok, now you've enabled your disconnect and you noticed strange sound coming out of the speakers or CRC-Errors while packing with WinRar? Time to turn some knobs a bit.
- try to enable as many PCI options as possible in the BIOS. Vcool or WPCREdit can do this from Windows. For my KT133, "Master Read Caching" is cruical. "CPU-to-PCI Write Buffer" and "Delayed Transactions" are also good tries. Note: Users of the VIA 686B-Southbridge shouldn't enable "Master Read Caching" and "Delayed Transactions".
- S2kCtl and CPUMSR have the option to change the "Bus frequency divisors". The lower they are, the less latencies in the system.
- CPUMSR additionally offers "clock change timing" settings. Here you can select to perform the change from low frequency to high frequency faster
- RMClock has some more advanced timing settings, also autostart
- get the latest BIOS. Your manufacuturer may have changed some other PCI settings

2. Older CPUs - K6, K5, Pentium III/II/I and so on

Those CPUs also support going to sleep while recieving HLT. There is no disconnection necessary. But the operating system has to supply a HLT command. Linux is okay, but Windows may not. You may need a program which replaces the idle thread and issues HLT commands.
- download KCPUCooler or WinCooler
- or search for "Rain" or "Waterfall" on google

3. Cool'n'Quiet equivalent for Athlon XP

Athlon XP CPUs since the Palomino/Morgan can be changed to be a mobile CPU. The main ressource for this mod is
It enables PowerNow! and works with nearly all chipsets except the nForce 1+2. Now you can adjust the multiplier under Windows. When you had an unlocked CPU before, you where previously not allowed to change the multiplier in Windows. When you had a "superlocked" CPU you are now able to change the multipliers in Windows only.

What are the advantages of this mod for the silent crowd?
Frankly speaking, not as nearly as many as with Cool'n'Quiet. The problem is that you can't change the voltage on the fly. Only nForce 2 boards are supporting this, but they don't support PowerNow! What a pitty, isn't it? You only have additional saving over "Disconnect on HLT/STPGNT" if you lower the voltage. So for now this tweak could be used as a cool geek toy or as a on-demand limiter of the CPU frequency when you want to have a little bit less noisier.
But the change of the frequency can also be done by other software by changing the FSB - even with a locked CPU:
8rdavcore for nForce2 users:

apr/02/05: CoolOn and KCPUCooler and WinCooler added
sept/01/06 RMClock added

Suggestions very welcome!

Last edited by jojo4u on Fri Sep 01, 2006 8:38 am, edited 11 times in total.

 Post subject:
PostPosted: Fri Apr 01, 2005 9:20 pm 
Friend of SPCR

Joined: Sun Dec 05, 2004 11:34 pm
Posts: 889
Location: Finland -- Folding For SPCR
Excellent post! 8)

very small addition to the cooling software is CoolON. Personally prefer it over other cooling software.

Just because I didn't respond to your post doesn't mean you were right. It just means I was speechless as to how to reply to such an idiotic statement


 Post subject:
PostPosted: Sat Dec 24, 2005 10:19 pm 

Joined: Tue Nov 25, 2003 10:24 am
Posts: 47
I only found this post after searching for many hours and finding s2kctl! BTW, there is a new version available, v1.5b103, dated 2005-12-04 (minor startup bug fixed).

On my MSI KT880 Delta-FSR (MS-7047) motherboard with an Athlon XP 3200+ at 2.2GHz (11x, 200MHz FSB) and SLK-900-A heatsink, enabling S2K bus disconnect reduced my idle temperature by at least 12C, and further changing the halt and stop grant divisors from 8 to 64 gained a further 2C or more reduction. That is a minimum idle temperature drop of 14C! Also note that there will still be a benefit, although reduced, at anything less then 100% cpu. Since I don't have an Athlon XP-M (XP Mobile) and did not want to modify all bridges, including max core voltage, s2kctl was the only option.

At least on this board, and with an Athlon XP, S2K bus disconnect seems stable. Some users report stability problems, sound issues, USB 2.0 issues with VIA chipsets, and problems with AMD non-Athlon XP processors. It appears that success or failure is related to using an Athlon XP procesor and the quality of your power supply and Vcore voltage regulator, as well as possibly RAM quality and PCI card compatibility. The PCI latency fix should resolve sound issues. I also found a note that suggested only full multipliers should be used (11x, 10x, ...) and not the half multiplers (10.5x, 9.5x, ...).

Unless you set s2kctl to autorun (Advanced->Miscellaneous) you can easily recover by rebooting. If s2kctl autoruns, just disable it in safe mode.

This article, "AMD Athlon XP 3000+, 2800+ and 2500+ on Barton Core" describes S2K bus disconnect and shows test results. This article, "Athlon Powersaving HOWTO", describes power saving in Linux, but provides some more technical detail on the chipset settings required if you want to use WPCREDIT.

 Post subject:
PostPosted: Sun Dec 25, 2005 8:17 am 

Joined: Tue Nov 25, 2003 10:24 am
Posts: 47
Executing 's2kctl/e' will apply the last settings and exit.
However the latest version does not seem to automatically reapply the settings on resume from standby in WinXP SP2.

 Post subject:
PostPosted: Sat Dec 31, 2005 7:46 pm 

Joined: Tue Nov 25, 2003 10:24 am
Posts: 47
I stopped using s2k bus disconnect (on a MSI KT880 Delta, MS-7047). I was getting a very annoying and extremely high pitched whine from some component surrouding the processor. It sounded like a very high pitched and fast bubbling noise. None of the components were particularly warm, and touching the coils did not stop it. Since I could not isolate this noise, and was concerned about damage, I'm back to high temperatures but no noise.

 Post subject:
PostPosted: Sat Feb 18, 2006 5:25 pm 

Joined: Sat Feb 18, 2006 5:14 pm
Posts: 1
I'm experimenting whit this soft-cooling, but in my configuration (KT133A and Audigy2) works correctly only when the "clock change timing" is set to "ultra-fast" in CPUMSR.
My question is if exits a tool to auto-set this bit on startup. :?: All soft-coolers autostarts the "Cloc divisor" only. :(


 Post subject:
PostPosted: Sat May 13, 2006 9:09 pm 

Joined: Tue Aug 23, 2005 1:53 pm
Posts: 1201
Location: Plymouth, MI
thats silly..i was linking to this thread and accidentally posted in it....

 Post subject: Re: P1 to Athlon XP software cooling & Athlon XP CnQ equival
PostPosted: Fri Jan 04, 2013 1:41 pm 

Joined: Mon Mar 17, 2008 1:49 pm
Posts: 1365
Location: UK
I know this thread has been dead for some years but I came across it when trying to resurrect an Athlon XP 2000+. Some of these software tools listed are no longer around or are in an unmaintained state now given their age.

My testing with a power meter showed some very interesting differences between three different operating systems. It is quite clear that just having the right operating system that supports ACPI is the best place to start.

Idle power consumption and CPU temp:
Windows 98SE: 137W, 57C
Windows XP: 121W, 52C
Arch Linux: 121W, 52C

Raijintek Metis: i5-6400, Scythe Ninja 4, Asus Z170i Pro Gaming, 8Gb RAM, GTX 950, Crucial 250Gb M.2, Seasonic X-400

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