Stupid XP-M question, please help with my ignorance

Tobias · Post by **Tobias** » Wed Aug 25, 2004 1:06 pm

I know that some XP-M chips run at 35 and 45 W, but does all of them do that? I am finaly in the market for a desktop replacement and are looking att different CPU:s, is there any good website listing all CPU:s available in a notebook? Since my budget is very restrictive a low power CPU is the ideal, but would rather fast loose in the race against my wallet. I would rather have a notebook with a hot CPU then no notebook at all....

nmuntz · Post by **nmuntz** » Wed Aug 25, 2004 4:55 pm

I was kind of wondering the same thing. I have a 2500XP-M that is rated at 45W. I underclock it to 800MHz and undervolt it to 1.1v so it likely doesn't dissipate more than 25 watts at full load.

On the web I see the odd 2400XP-M rated at 35W so I'm wondering if this is the same chip as the 2500, or one that runs even cooler.

Edward Ng · Post by **Edward Ng** » Wed Aug 25, 2004 5:07 pm

All of them are techically the same chip (Barton core). I am running the 35watt Mobile 2400+ in my water-cooled overclock rig. The stock settings are 13.5*133=1800MHz at 1.35Volts and my motherboard, ABIT AN7, can't even go that low; its minimum voltage setting is 1.375Volts. I have it running at 211*12.5=~2640MHz at 2.156Volts, however.

All the Mobile Bartons with wattage ratings are based upon their TDP heat rating. For example, my 35Watt Mobile Barton, at stock clockrate and voltage, are calculated to put out approximately 34.6watts TDP and up to 44watts MP. As soon as the clockrate or voltage are changed, those figures get thrown out the window. So, now that my chip is being fed 2.156Volts and running at 2640MHz, it is dumping about 114.4Watts TDP into my water system on a normal basis and up to about 145.6Watts MP under full load!

So for Tobias' question, yes, they can all do that; however, the desktop Barton cores are mulitplier locked, so the only way to underclock them is via your FSB setting. The Mobile Bartons (models with the wattage ratings) do not have locked multipliers, as they change multipliers to save energy on laptops that support this feature. I am not sure if there's a site listing all chips available, but NewEgg is the best source I know of to purchase the Mobile Bartons; it's where I got both, my 45Watt 2500+ and my 35Watt 2400+.

As for nmuntz, the answer to your questions is that yes, they are the same exact, "chip." They literally come off the same wafer at the fab. AMD bins the chip cores, and the ones that can run full speed at lower voltages are binned off for Mobile application, and then their FSB, multiplier and voltage are set via the bridges on the packaging of the final chip. The bridges are set differently, but the cores are precisely the same. All Barton cores behave precisely the same, heatwise, when set to the same voltage and core speed (give or a take 5-10% due to manufacturer inconsistency. Nothing in the real world is absolutely, positively dead-on, and minor variations in manufacturing will yield up to 10% higher or lower thermal variation between two otherwise identical chips from the same wafer).

And just so you know, at 800MHz and 1.1Volts, you're looking at only about 14.9watts TDP and nearly 19watts MP!

-Ed

EDIT: Typos.

silvervarg · Post by **silvervarg** » Wed Aug 25, 2004 11:10 pm

I have heard about idle watts, typical load watts, max load watts and TDP (thermal design power), but what is watts MP?

Edward Ng · Post by **Edward Ng** » Thu Aug 26, 2004 5:25 am

MP is your max load watts.

vortex222 · Post by **vortex222** » Thu Aug 26, 2004 9:06 am

if you can find an old laptop based on the tbred 1700 LV then its rated for about 25 watts. some old Compaq presario 2100 used them, and are a very cheap and feature rich laptop. decent battery life, but crap video proformance. (ati igp320)

i bought a 2197ca based on the mobile athlon 2800 and found that when the laptop was set to use the powernow, it released very little heat. there are also some 2198's that use the mobile 2500. that woudl be even better then the 2800 in my opinion, as its much cooler at stock

the 2800 XPm is 2.166 ghz at 1.55 volts.

silvervarg · Post by **silvervarg** » Fri Aug 27, 2004 5:03 am

MP is your max load watts.

Bt according to your calculations you manage to get max load watts far beyond AMD's TDP. So far I have never seen an AMD CPU that puts out more watts than the TDP. (Intel is wastely different).

Edward Ng · Post by **Edward Ng** » Fri Aug 27, 2004 5:30 am

These calculations were done by CPUBurn--I can only guess that CPUBurn is accurate, but I don't know of a particular way to know for certain that CPUBurn is right or wrong.

If it's in error, at least it's over, rather than under. Anyway, that's why I always list both, TDP and MP--you guys can use whichever figure you find more appropriate for your usage pattern, configuration or purpose.