With the release of the FX53, AMD finally has a CPU with a default frequency over 2250Mhz. They also seem to be using the new refined process on the new Athlon XPs, evident by the newest ones coming out of the fab, the Mobile Athlon XPs. While not everyone is willing to drop a big chunk of change on the FX to see the benefits of the newest stepping, you'd only need $80 - $100 to play with a new Mobile XP.
With the new 'CG' stepping of the FX53 and the newer A64s, 2.5 -2.6Ghz on air isn't uncommon, the same holds true for the Mobile Athlon XP. But will they run in SMP on the Dually? A pair of 2.5Ghz chips would be a nice boost to the aging and dieing MPX platform. It's been done by a few already, but the Mobile Athlons are a little different than the desktop Athlon XPs, so we're going to see how to get them up to speed.
The following is the L5 bridges of a Barton 2800MP, a Duron Applebred 1800Mhz, and a Mobile Athlon 2600. I don't have an Athlon XP ATM, but the bridge layout is the same as the Duron, so they are interchangeable of this demonstration.
There are four L5 bridges, the last L5 is the one that enables/disables the SMP function of the AMD Athlon chips. If you look at the real MP chip you'll see that the last one is closed. To enable the SMP function of the AthlonXP you simply closed the last L5, that you can see open on the Duron/XP. Now if you look at the Mobile chip you will see that the last L5 is already closed, just like the Barton MP, also that the third L5 is also closed were as the other chips it's not. That's the bridge that controls the chips PowerNow function of the Mobiles and why the chip has to be unlocked to be able to use it.
Since the Mobile is already has SMP enabled, I decided to drop them in without disabling the PowerNow bridge to see what happens. It booted up fine but I got a warning that the chips where not SMP capable and it would continue to load in uniprocessor mode. The same thing happens if you drop in two XPs, or your L5 connection isn't making good contact. But in fact the OS saw both of them, and running a few benchies confirmed that both CPUs were indeed running. Even though they are detected as Mobile XPs
To fix that you have to cut the third L5 bridge on the Mobile, the one that makes it a mobile, the PowerNow bridge. To do that I used an exato-knife. A razor blade or any sharp pointy knife will do. Since my eyes don't have a 40X macro zoom like my camera, I used a magnifying glass so I could see what I was doing. Placing the knife on the third L5, just press gently down into the substrate until the bridge is cut. You can almost feel it when it gives way. Another good idea is to hold the knife with the tip facing the fourth or last L5, that way you won't cut it if you go to deep. So when you’re done it should look just like the real BartonMP, like this
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Presto! Two MP chips. But now we have another problem. The Mobile Athlon 2600+ has a default multiplier set to 6X, because of its PowerNow Technology. The L3 bridges control the default multipliers on all Tbreds and Barton CPUs.You can see that the second and third L3s are cut, hence you have a 6X chip. You can look at the chart HERE for all the default host clock multipliers and their L3 settings. That's all fine and well on a board with multiplier adjustments in the BIOS, but most dual motherboards don't, and the one that does, was only half assed implemented and only works to 12X, which isn't going to help in this case.
So we'll just have to change the multiplier. Before that fateful week in the middle of September 2003, all AMD Tbreds and Bartons were unlocked. After week 40 they were internally locked, so that manipulating the bridges no longer worked. A bit before they were "locked" AMD also changed the substrate on the chips, throwing in some new fake contact points and covering the real contact points with a waxy coating so it was harder to get at. You can see the difference in the dies in the picture above, the 2800MP is the older one and the Duron and Mobile are with the newer substrate. AMD said that they took these measures because it was too easy to change the chips as some unscrupulous resellers where doing. Guess it's just a coincidence that the A64s were launched right around week 40 of last year and they are unlocked
I use to just cut and close the L3s to the multiplier that I wanted, you can see that I changed the default of my 2800MPs to 15X from 16X so I could utilize a higher FSB. The newer chips need some more work, uncovering the real contact points, removing the waxy covering....So this time I decided to change the multiplier by grounding and opening the L3s pins from underneath the CPU. Don't have to mark up the chip and won't kill it if you slip. The Bartons and Tbreds use the AJ27, AL25, AN25, AL27, AN27 pins on the chips for the multiplier. Another great site with invaluable info HERE I decided to use a 16X multiplier to test with first. You can look HERE to get a socket view of were the host clock multiplier pins go. For wire I used and old CDROM audio cable, you could alternatively cut up an old IDE cable.
Plenty of wire there Grabbing a piece of the wire with a pair of needle nose pliers, I cut it with a razor knife, about 5mm. Then just fold it over until you have a nice little "U" shape.
Then drop it into the corresponding socket holes for the AJ27, AL25, AN25, AL27, AN27 pins, for the multiplier that you want. This is what a 16X multiplier looks like when the socket is done.
And this is the final fruits of your labor. Two Barton MPs running at 2600Mhz on air
Hope this was helpful for someone thinking about building a cheap duallie or someone can get a little more life out of their MPX board.