If you remember, Athlon and Durons while not officially supporting SMP and thus 2-way processor setups, they did have SMP support enabled and could be used in AMD dual motherboards. Same goes for the initial batches of AthlonXPs. However, AMD then disabled that feature, so all new AthlonXPs would not work in dual motherboards. Thus only Athlon (T-bird), early AthlonXP (Palomino), Durons and Athlon MP processors work. But there is a way round it.


Athlon XP (Palomino)



By connecting the 4th L5 bridge (farest away from the L5 text as highlighted in the pic), SMP seems to be enabled again and can be used in dual motherboards. To multipler unlock, all the L1 bridges need to be connected.


Athlon XP (T-bred)



The 4th L5 bridge trick supposedly works for the AthlonXP (T-bred) too. The 4th L5 bridge on the T-bred is now nearest the L5 text (which is the one highlighted in the above pic). Once connected, SMP should be enabled. Not sure if there are any BIOS issues, being a T-bred and all, so best to use the latest BIOS. To multipler unlock, the L3 bridge highlighted in the pic needs to be connected.

Athlon XP (Barton)

Seems the Barton can also be modified to enable SMP. Exactly the same as the T-Bred, the 4th L5 bridge (nearest the L5 text and the rightmost bridge in the L5 row).

Since Bartons are based on 333FSB (and now 400FSB), you also might need to modify the multipler to a suitable one for running at 266FSB (ie, higher), so the clock speed is exactly or slightly lower than the default. Since most dual-boards don't offer multiplier adjustment (or only up to 12.5x), you'll have to modify the L3 bridges to change the default multiplier. Unless the processor's default multiplier is already 13x and the motherboard lets you change the multiplier to values above 12.5x (either directly or via remapping 5-12.5x with +8x).

For the XP2800+ (12.5x166, 2.083GHz) it's suggested modifying the default multiplier to 15x. So you cut the 5th L3 bridge to enable the upper range multipliers (13x and above). If your motherboard lets you select the multiplier you could try selecting 15x or if the max is 12.5x, try 7x to see if enabling the upper range 5th bit, has remapped the 5-12.5x multipliers with +8x (ie 7x+8x=15x). If not, then you'll have to change the other L3 bridges to set the multiplier value manually. Connecting the 1st, 2nd and 4th L3 bridges on an XP2800+ should give you the 15x multiplier value (assuming the 5th L3 bridge is already cut). That should give you 2.0GHz (15x133), which is just under the default for a XP2800+ (there is no 15.5x multiplier on Bartons to set, so 15x is the closest). Once everything is up and running, you of course can still overclock via the FSB and multiplier if the dual motherboard allows it.

However, according to the below article, Bartons with SMP enabled only work on certain dual AMD boards and even then, with only certain BIOSes. For example, they seem to work on the MSI's K7D Master, but only with BIOS 1.3 or 1.4B3. Any BIOS higher than those seem to have problems running Bartons in SMP mode, even after they had been modified correctly.

<a href='http://www.hardwarezone.com/articles/articles.hwz?cid=2&aid=747' target='_blank'>http://www.hardwarezone.com/articles/artic...z?cid=2&aid=747</a>

Supposedly some have had success with the mobile AthlonXP-Ms, but some have said certain boards also require the 3rd L5 Bridge (PowerNow) to be open/cut.

Because some dual AMD boards lack multiplier adjustment options, it might be of interest that in Japan you used to be able to get the <a href='http://www.overclock2.co.uk/forums/index.php?act=ST&f=13&t=1458&hl=&s=' target='_blank'>Kurouto Shikou</a> SocketA overclocking device. Which would sit inbetween the socket and processor and let you select the multiplier via dip switches. Think there was one for the older Athlon T-birds and Duron Spitfires (<1GHz) and one for the new AthlonXP and Duron Morgans (1GHz+). Not sure if they are compatible with T-Bred and Barton AthlonXPs though. Could just be for the Palominos.

Are there any benchmarks that show dual Bartons vs dual Athlon MP at the same speeds? I havn't found any but it would be interesting to see the comparison.

-Mark

Haven't seen any extensive benchmark comparisons no. But then the Bartons are the hardest to mod and no real new dual AMD boards to get the main review sites interested in doing so I guess. However, there are a few benchmarks here, comparing the T-Bred and Barton in both single and dual configurations:

<a href='http://www.hardwarezone.com/articles/articles.hwz?cid=2&aid=747&page=4' target='_blank'>http://www.hardwarezone.com/articles/artic...&aid=747&page=4</a>

Really only in one or two of the benchmarks did the 512k L2 cache of the Barton result in an improvement in performance. But then that's only out of like 4 benchmarks tested. So all you can say, is that the 512k isn't going to always overcome the MHz gap between it and the T-Bred. So unless you overclock the Barton to T-Bred speeds or use the high speed Bartons, it really depends if the apps you use benefit from more L2 cache or not.

Seems there is another overclocking SocketA device on the market for AMD Athlon XP/MP processors:

<a href='http://www.upgradeware.com/english/product/xptmc/xptmc.htm' target='_blank'>http://www.upgradeware.com/english/product...xptmc/xptmc.htm</a>

Supposedly allows full multiplier adjustment (5-24x) WITHOUT the need for modify any L bridges, as long as the processor is 'mulitplier unlocked' (ie all L1 bridges connected - factory default for T-Bred/Barton). So can be used for overclocking or running 333/400FSB processors on boards that only support 100/133MHz FSB. Processor wise, supposedly it supports:

AthlonXP - Thoroughbred, Barton & Thorton
AthlonMP - Thoroughbred & Barton


Review:

<a href='http://www17.tomshardware.com/cpu/20030703/index.html' target='_blank'>http://www17.tomshardware.com/cpu/20030703/index.html</a>

hi i have read about this product seems good.please could you tel me if this would improve my 2600+ barton?

which i think is unlocked anyway as i can change the multi on my board and the cpu now says its a 2800+ with the multi on 12.5 as thats the highest that my GA-7VAXP wil go. so if i spent the money on this thing how would that improve on my board as the multi will not go any higher??

thanks....

It should let you access 5-24x multiplier (instead of your current 5-12.5x), as it will bypass the limit on your motherboard. Assuming your processor is already multiplier unlocked.

Although you can enable the multipliers above 12.5x manually by doing the L3 bridge mod to your unlocked processor. That would then let you select 13-24x using your motherboard, instead of 5-12.5x. But if you wanted to use anything below 13x again, you'd have to undo the mod.

thanks very much mate i will think anbout this mod...

does this mean i could get another 2600 xp-m and have dual 2.6ghz on a different board?

In theory yeah, assuming you can still SMP-enable XP-Ms and you can find a dual-socketA board and BIOS that works with them.

But it's not really that practical. The only dual-socketA boards are old AMD760-MP/X boards, that don't support modern features and probably aren't made anymore. They never had good BIOS options (FSB, multiplier, voltages, memory), so not very overclockable and might have to set them by cutting/connecting L bridges which is not easy. Unless you could find a SocketA overclocking device mentioned above, if they still exist.

Damn

ok i shall search !!

2 x XP3200s @ 2.5Ghz would be sweet

shame the boards are out of date

the mods not hard did it to mine ...... with a pencil! and it worked.... but went back to normal i.e. used a rubber cos had no need for a dual processor enabled chip!

its just finding a decent board because they are old