Great news for KT266A owners!

Hi to everybody,

The short story is: <b>Barton with KT266A WORKS!</b>


This post if for anyone with a KT266A mobo. In fact, I have only tested with mine, Epox 8KHA+, but I suppose what is important is chipset capabilities, so probably applies to all KT266A mobos. Even other chipsets may behave similar.

I have always thought that a Barton would be a nice last upgrade for my rig, but I was afraid of to issues: compatibility and multiplier.

Right now all of you are aware of mobile Bartons and how good they are. Being multiplier locked AND running at 266FSB, gives the best options to run flawlessly on my computer.

Anyway, I take no responsaiblity for whatever happens to anyone trying this, etc, etc, etc. :wink:


So I bought two Barton 2400+ 266FSB (only $77 each on Newegg)

After replacing my XP 1700+ with Barton 2400+, I power up my computer. I haven't last BIOS, and this caused a "Unknown CPU" at post, BUT computer start up with no problems at all. The only difference with Paly/TBred (added L2) doesn't cause any problem, and this confirms my theory.

WCPUID didn't recognize the CPU, BUT identifies 512Kb L2. The same with SiSoft Sandra. Computer was running with NO problems at all.


If Auto is selected, x6 multiplier is the default. Running at 133FSB (official max for KT266A) gives a 800Mhz CPU. Yes, quite sad at the moment :frown:

But after playing some combinations, I ended up with a maximum of x12.5 when selecting x13. Selecting x14 and x15 ended up with x6. Flashing to the latest BIOS didn't change the result. Just mention that after flashing the CPU becomes "K7" instead of "Unkwon"

I used to run it my XP 1700+ at 150FSB, as I don't want to go higher due to risk with data corruption and problems with PCI cards. So currently my final setup is 150 x 12.5 = 1875Mhz

About voltage, I don't know why in BIOS the default says 1.575, I can change it to -0.1 so ended with 1.475, even Motherboard Monitor and others say 1.5 is where I am. Anyway, still far from standard 1.65 for normal Bartons and even lower than my previous 1.75 (Palomino)


Having a maximum of x12.5 multiplier is sad. But I have managed to find a <A HREF="" target="_new">utility</A> that can change multiplier once in Windows. Great! I thought. The utility identifies my CPU as "supported" for changing multi and voltage, but is not working for W98. The developer is working on this issue. Anyway, thanks a lot! <A HREF="" target="_new">Here you have a link to the main page</A>

So if anyone want to try it with Windows XP and confirm that it works, that would be GREAT!


IMO KT266A mobos will be able to run any Barton, but obviously not with any multiplier. Mobile Bartons are the solution, and a very cheap one, only $77.

Is NOT necessary that BIOS identifies the CPU. Even with an "Unkwon CPU" works perfectly. Anyway, there is always a risk if you try with another mobo (remeber, mine is a 8KHA+). Please provide feedback to this post in order to create a "compatible barton mobile mobos" for everybody.

Finally, even at x12.5 I am quite satisfied. But again, feedback for Windows 2000 or XP running CPU MSR utility (or another one) would be great as this would open overclocking capabilities to old modos. And ensure I can go further when I update my OS!

Hope this helps and answer some questions.

Still looking for a <b>good online retailer</b> in Spain :frown:
4 answers Last reply
More about great news kt266a owners
  1. Old news but a nice reminder for people still using old mobos.

    Just so you know there used to be more options (and maybe there still are) than what you have done.

    I'm using an even older mobo with a much older chipset, Epox 8KTA3PRO, KT133A. For a year I've been using an XP1700+ (Tbred B) mod'd to be an XP2400+. I run it at 140 Mhz with a 15x multiplier. Yes, I said 15x.

    The key was you needed a fully unlocked chip and one with the 8X multiplier bit enabled. With Tbred B's and the early Bartons it was possible to run on KT266A, KT266, KT133A, and even KT133 (No "A") motherboards at full speed. Of course, you could not run full FSB speed on some mobos but you could still run the CPU at full speed (or higher).

    My "XP2400+" has worked on my present board at 14 x 150 (wire mod eventually failed, still working on that issue), with my current config of 15 x 140, and also at 20 x 100 = 2000 Mhz with a fairly convervative VCore setting of 1.8 volt. I have pushed higher reaching my max overclocks at 22.5 x 100 = 2250 Mhz, 15 x 150 Mhz = 2250 Mhz, 17 x 133 = 2267 Mhz. All of my max overclocks required an unsafe Vcore of 2.15 volt. (The 8KTA3PRO can go up to 2.25 volt). This is too high with air cooling.

    I've put the very same mod'd processor into my even older Abit KT7 (KT133). It ran fine at 20 * 100 = 2000 Mhz at 1.85 volt. I could not push any higher as that is the max VCore for that mobo.

    Unlocked Bartons worked just as well (for other people). Just cut the L3-3 and L3-5 bridges on an unlocked XP2500+, changing the default multiplier from 11x to 13.5x, and then the high multipliers are enabled. (Don't try it! It won't work on your "super locked" Barton).

    There were/are other tricks involved.

    - Processor must be unlocked. (Present Bartons, Thortons, and Applebreds are no good. They are "super locked").

    - 8X multiplier bit must be enabled (ie processor must have a multiplier of 13X or higher, or must be mod'd to have this)

    - On legacy VIA mobo multiplier remaps, 15x up to 24x, (see table below) work fine when FSB is 100 mhz to 124 mhz but mods may be necessary for 133 Mhz and higher.

    - Due to legacy multiplier circuits, most legacy VIA boards can't use multipliers 13x, 13.5x, 14x. There is a mod for this problem.

    - Legacy Abit boards have an extra issue. When using the remaps they by default try to POST at 20 * 100 = 2000 Mhz. For some chips this was too much of an overclock at default voltage most notably Tbred A.

    Check Usenet for more information. I learned that Epox released a Beta BIOS for my mobo. Now my processor is detected as "XP2600+" which I guess it should be since it's running at 2100 Mhz.

    We the owners of old motherboards have one last hope, the so called "mobile mod". By closing the 2nd to last L5 bridge you turn your Barton (or Tbred, or Thorton, or Applebred) into a mobile XP. This makes it possible to change multiplier on the fly. I'm looking for info on what range of multipliers are available and what the success rate is with legacy motherboards.

    Take a look at the following links which have lots of good information regarding installing new processors in old mobos including mod'ing and workarounds for problems.

    <b>Overclocking and mod'ing</b>

    <b>Workarounds for problems with legacy boards</b> (mostly VIA chipsets)

    <b>Here's the multiplier remap table.</b><pre><font color=purple><b>Bios Remap (8X bit must be enabled)
    or Bridges</b>
    5x ----> 13x (doesn't work on some mobos)
    5.5 ----> 13.5x (same)
    6 ----> 14x (same)
    6.5 ----> 21x (same)
    7 ----> 15x
    7.5 ----> 22.5x
    8 ----> 16x
    8.5 ----> 16.5x
    9 ----> 17x
    9.5 ----> 18x
    10 ----> 23x
    10.5 ----> 24x
    11 ----> (reserved)
    11.5 ----> 19x
    12 ----> (reserved)
    12.5 ----> 20x</font color=purple></pre><p>
    <b>56K, slow and steady does not win the race on internet!</b>
  2. Thanks a lot phsstpok!

    If I understand correctly, I need to mod the mobile CPU in order to select from x13 and up. I have been looking to the links you provide ... I'm not an expertise, but I guess what I have to do is close the last L3 bridge (on teh right side) with conductive silver or similar to enable a x8 "switch multiplier". Am I right?

    Anyway, BIOS will still show x8 when it really sets at x16, but the end result will be the desired, correct?

    Still looking for a <b>good online retailer</b> in Spain :frown:
  3. Quote:
    If I understand correctly, I need to mod the mobile CPU in order to select from x13 and up. I have been looking to the links you provide ... I'm not an expertise, but I guess what I have to do is close the last L3 bridge (on teh right side) with conductive silver or similar to enable a x8 "switch multiplier". Am I right?

    You shouldn't have to mod a mobile XP. Remember these are 133 mhz parts. The mobile Barton XP2400+ and XP2500+ should already have high multipliers. The mobile XP2200+ should also have a high multiplier.

    In theory, the mobile procs should work just like their unlocked desktop equivalents. However, I'm waiting for confirmation that the multiplier remaps have been implemented in Mobile XP's.

    LHGPooPaa already told me that it does not work on his KT333 motherboard. He gets straight multipliers with his mobile XP2500+. No remaps. This limits him to 12.5x in BIOS. Using soft multipliers he's limited to 14x.

    We don't know why he has these limitations, so far we don't

    Perhaps the KT333 chipset doesn't use remaps.

    My advise is hold off for now or try to locate an unlocked desktop Barton or Tbred B.

    <b>56K, slow and steady does not win the race on internet!</b>
  4. Thanks again. Right now I will continue with 12.5 x 150 until I upgrade to WinXP or find some software to change multiplier.

    Anyway and as I have already told, I'm happy for now!

    Still looking for a <b>good online retailer</b> in Spain :frown:
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